Bulletin of the Museum of Comparative Zoology, AT HARVARD COLLEGE. Vou. VE Nos-8, 9. No. 8. LETTER No. 4. To 0. P. PATTERSON, Supt. U.S. Coast Survey, from ALEXANDER AGASSIZ, ON THE DREDGING OPERATIONS OF THE U.S. COAST SURVEY Sr, ° BLAKE,” i: DURING JUNE AND JULY, 1880. No: 9. a DESCRIPTION OF GRAVITATING TRAP, sy Lieut.-CoMMANDER ee BS C. D. Sicsper, U.S.N. 7 CAMBRIDGE: PRINTED FOR THE MUSEUM SEPTEMBER, 1880. - Museum of Comparative Zodlogy, Cambridge, Mass. Wirth the compliments of ALEXANDER AGASSIZ. Gua AM Bas ) aa inert , a mney apeyanter: bet te-7- Mm. 4 e wee £ § Ehret No. 8.— (LeTTER No.4.) Zo Caruite P. Patterson, Superin- tendent United States Coast and Ceodetic Survey, Washington, D. C., from ALEXANDER AGASSIZ, on the Dredging Operations carried on during part of June and July, 1880, by the United States Coast Survey Steamer “ Blake,’ Commander J. R. BARTLETT, U.S. LN. I so1nep the “Blake,” at Newport, late in June. According to your instructions, we proceeded to the northeastern edge of George’s Shoal, where we ran our first line of dredgings from the 100-fathom line to a depth of nearly 1250 fathoms. Our second line was run to the south- east, off Montauk Point. This was interrupted’ by bad weather. We were compelled to put into Newport, and completed the line on our return from the South. This line extended to nearly 1400 fathoms. On leaving Newport for the second time we steamed directly for Charleston, S. C. A line of dredgings was run from the 100-fathom line normal to the coast directly across the Gulf Stream to a distance of about 120 miles to the eastward of Charleston. Finding that our depth did not increase at that distance, — our greatest depth not being much more than 350 fathoms, —Commander Bartlett thought it prudent to return towards shore, to the so-called axis of the Gulf Stream, and to run a line in a northeastern direction parallel to the coast in the trough of the Gulf Stream. To our great astonishment the depth did not in- crease. We carried from 250 to less than 300 fathoms until we nearly reached the latitude of Cape Hatteras, when in a short distance there was a very rapid drop from 352 fathoms to 1,386 fathoms. A fifth line was run normal to this northern slope of the Gulf Stream plateau, to a depth of 1,632 fathoms. A sixth line was run to the northward of Cape Hatteras, to a depth of 1,047 fathoms. A seventh line was run east off Cape May, from the 100-fathom line to nearly 1200 fathoms. We were greatly disappointed in the richness of the fauna on the lines off Charleston and in the Gulf Stream, owing partly to the very gradual slope of the continent towards deep water, and the strong cur- rent of the Gulf Stream, which sweeps everything off the bottom along its course. There is but little food for the deep-water animals, and it was only along the edges of the Gulf Stream where mud and silt accu- VOL. VI. — No. 8. 148 BULLETIN OF THE mulated that we made satisfactory hauls on our Southern lines. What was obtained seemed to be a scanty northern extension of the fauna of the Caribbean Sea and of the Gulf of Mexico between the 100 and 350 fathom lines. It was not until we trawled on the steep slope of the Gulf Stream plateau south of Cape Hatteras, where the bottom was fine mud and Globigerina ooze, that we made a rich harvest again, in striking contrast to the poor hauls along the well-swept rocky or hard bottom of the Gulf Stream to the southward. Along the western edge of the Gulf Stream we came upon several patches of the modern green-sand forma- tion, where the bottom was entirely composed of perfectly clean dead Globigerine. Although Pteropods were very common at the surface all the way from Charleston to Cape Hatteras, they were only rarely brought up dead from the bottom ; but when the steep slope south of Hatteras was reached they again assumed a prominent part in the composition of the bottom mud. While running the line parallel to the coast from off Charleston to Cape Hatteras, we came twice upon localities where the sounding cup brought up nothing but clean Globigerinze, the bottom consisting en- tirely of the modern green-sand to which Bailey and Pourtales had already called attention as forming off shore on the Atlantic coast of the United States. The rapid changes in the character of the mud, as we increase both our distance from shore and the depth, are well shown in the nature of the bottom of the different depths along the short, steep line forming the northern slope of the Gulf Stream plateau traced by the “Blake” from Charleston to south of Cape Hatteras. We very rapidly pass from the comparatively coarse mud to fine and finer ooze, which becomes an impalpable silt in the deeper water beyond 1,000 or 2,000 fathoms, assuming at the same time gradually a lighter color. Among the Tunicates I may mention two new species of Salpz, one of which is interesting, its chain occupying an intermediate position between that of Salpa pinnata and the ordinary Salpa chain of 8. zo- naria or S. Cabotti of our coast. The solitary individuals are gigantic specimens, measuring no less than twelve inches in length. This solitary form is: closely allied to S. maxima, but differs from it in the number and arrangement of the muscular bands. The chains grow to a great length, some of them measuring more than ten feet in length and as much as nine inches in breadth. The zodids are arranged as in S. pin- nata, side by side in a single row, extending vertically across the whole width of the chain, and forming a thin ribbon, which when floating is usually slightly coiled like a tape. The zodids of the chain resemble MUSEUM OF COMPARATIVE ZOOLOGY. 149 S. Africana. This species was found at sea from Cape Hatteras as far north as the eastern extremity of George’s Shoal. Among the Acalephs, the most interesting form was a species of Do- decabostricha, Br., the largest specimen measuring no less than nine inches in height. Several specimens of a dark violet (claret-color) were brought up in the trawl, and it is very probable from the systematic aftin- ities of this Medusa that, like its allies, the Rhizostome, it lives on the bottom, rarely coming to the surface. For the genus Dodecabostricha Professor Agassiz established a new family, the Brandtide, and placed it in the vicinity of the Charibdeidee. While it undoubtedly has a general resemblance to the Charibdeide, the structure of the genital pouches and of the lobes of the actinostome shows that it is intermediate between the Aureliz and the Rhizostomz proper, combining at the same time structural features only found in the Pelagia. It is not known where Mertens found the species which is figured in Brandt’s memoir. As we trawled mainly on mud or clay bottoms, but few Hydroids were col- lected. All along the course of the stream we found large quantities of Tri- chodesmium erythreum. On one occasion, north of Hatteras, we passed through an extensive patch of this pelagic Alga, which colored the surface of the sea a dirty yellow for a distance of about a quarter of a mile by a hundred yards in width. Among the corals a fine species of Flabellum, probably the Flabellum alabastrum, Mos., and a few species characteristic of the West India seas and of the Gulf of Mexico were found to extend as far north as Cape Hatteras. There were a number of Pennatulee and Virgularie collected, probably the same species already described by Professor Verrill from the collections made by the United States Fish Commission, as well as a few Gorgoniz, among which I may mention numerous specimens of Kera- toisis. The Pennatulz and Gorgonie were all remarkable for their bril- liant bluish phosphorescence, a single Pennatula lighting up a large tub of water. A couple of species of Zoanthus were found in deep water. Among the Actiniz large specimens of Bunodes and of Edwardsia came up from depths of from 600 to 800 fathoms. Among the Echinoderms all the way from Cape Hatteras to the ex- tremity of George’s Shoal, Ophiomusium Lymani were quite common in deep water. Kchinus norvegicus is abundant, and Schizaster fragi- lis extends from deep water inside the 100-fathom line. A species of Asthenosoma and one of Phormosoma were also found in deep water, having the same general distribution as Ophiomusium. A fine species 150 BULLETIN OF THE of Urechinus closely allied to Urechinus naresianus, and several of the rarer species of Starfishes, — Archaster, Porcellanaster, Luidia, Astro- gonium, Porania, Pteraster, and Hippasteria, — were found to extend far into deep water; and beyond 1,000 fathoms, off George’s Bank, we found several fine specimens of Brisinga, as well as three or four species of the remarkable deep-sea Holothurians belonging to the or- der of Elasmopoda; among the Crinoids, Comatula Sarsii? and a few specimens of Rhizocrinus. Although the line to the eastward of Charles- ton, S. C., was commenced off the very home of the Scutelle and other Clypeastroids, it is remarkable that not a single Mellita or Clypeaster was dredged up, either on that line or the line run in the axis of the Gulf Stream as far as Cape Hatteras. Hchinarachnius off George’s Shoal was found to extend to a much greater depth, living specimens having come up in the trawl from a depth of 524 fathoms. But few Annelids were collected, a few specimens of Nemerteans, and of Calymne; one of the large Eunicide, the tubes of which, sometimes fully fifteen inches in length, often filled the bottom of the trawl when dragging on muddy bottoms, was specially numerous. A number of species of Cephalopods, mainly Northern species already found in shallower waters by the United States Fish Commission, were brought up, many of them from considerable depths. The Gasteropods and Acephala were represented by many of the species collected by the “Lightning” and ‘‘ Porcupine,” and by the United States Fish Com- mission. Among the Crustacea the most characteristic types were the gigantic Pygnogonidze, a species of Willemoesia, a couple of species of Gnatho- phausiz, Scalpellum, and large Amphipods. Among the Fishes a large collection was made, mainly of Macrouride, including a few new genera, which will be described by Mr. Goode, of the United States Fish Commission. We found cod, extending to a depth of over 300 fathoms (off George’s Shoal). Myxine and Lophius were brought up from 360 fathoms, as well as Sebastes norvegicus. A species of Phycis, from a depth of 233 fathoms, was found to be electric, giving quite a strong shock to Commander Bartlett and myself. It is a small species, about nine inches in length, of a light ashy violet color, with dull yellowish spots along the sides. The absence of siliceous and other sponges in the collections made during this summer is very striking, and although the number of speci- mens of certain species was often very great, yet the continental faunz of the northern part of the east coast of the United States is poor when MUSEUM OF COMPARATIVE ZOOLOGY. 151 compared to the wealth of species found in the Caribbean Sea and Gulf of Mexico during the former cruises of the ‘ Blake.” Commander Bartlett did everything in his power to make up for the absence of my assistant, and I was fortunate in again finding on board the older officers of the “ Blake,” Messrs. Sharrer, Jacoby, Peters, and Reynolds, whose industry, energy, and interest in the work has never flagged, and who have now attained a proficiency in deep-sea dredging hardly deemed possible three years ago. Lieut. Mentz and Dr. Persons joined the “Blake” during the winter of 1879, and Mr. Duvillard was attached to the “ Blake” as recorder during the first part of our cruise. During this short cruise we made no less than fifty hauls: we accom- plished nearly as much as during the three months of the first cruise in the Gulf of Mexico. As the greater part of the collections made during this cruise of the ‘‘Blake” cover the extension into deep water of the ground already in part occupied by the United States Fish Commission, I have arranged with Professor Baird to send the bulk of the collections made north of Cape Hatteras, for final study, to some of the naturalists to whom the collections of the Fish Commission have been intrusted. During the winter of 1879-80, Commander Bartlett, while sounding in the Western Caribbean Sea, made some twenty hauls with the trawl, dredge, and tangles. These collections, made incidentally by the officers of the “Blake,” show the extension of the continental fauna of the Eastern Caribbean to its extreme western portion. Pentacrinus was found off Santiago de Cuba, and off Kingston, Jamaica. The deep-water fauna was found to be the same as the deep-water fauna of the Eastern Caribbean. . Mr. Bartlett showed that a strong current passing over a ridge, as in the case of the Windward Passage between Cuba and San Domingo, swept it entirely clean, so that but little animal life was found to live upon it. But immediately beyond this, on the Caribbean side, the mud and silt are deposited in great quantities and animal life becomes plenty again. This, as I have stated above, was also our experience during the present cruise of the “Blake,” while dredging along the so- called axis of the Gulf Stream. Lieut.-Commander C. D. Sigsbee accompanied us on the “ Blake,” to superintend in person the first trial of his collecting cylinder. It was sent down in 30 fathoms, from 5 to 25 fathoms, with quite a fresh breeze blowing, at about eleven in the morning, in full sunlight,—a time when, with a smooth sea, the pelagic animals would all have been found 152 BULLETIN OF THE on the surface. The cylinder was found to work most satisfactorily, and brought up a few Calani, Hydroid Meduse, such as usually occur at the surface. A few slight modifications were suggested by Mr. Sigsbee, and Commander Bartlett recommended the addition of a wire-gauze trap, to facilitate the washing out of the microscopic animals which might be collected. we On the Ist of July the Sigsbee cylinder was tried for the second time in Lat. 39° 59’ 16” N., Lon. 70° 18’ 30” W., in 260 fathoms of water. The surface was carefully explored with the tow-net, to see what pelagic animals and others might be found on the surface. There were found Calanus, Sagitta, Annelid larvee, Hydroid Medusz, Squille em- bryos, Salpz, and a few Radiolarians. The cylinder, filled with water -which had: been carefully sifted through fine muslin, was then attached to the dredging wire, and lowered, so as to collect the animals to be found between 5 and 50 fathoms. The time occupied by the cylinder in passing through that space was 28 seconds. The cylinder was then brought up, and the sieves and gauze trap carefully washed with water, which had also previously been strained through fine muslin. The water was carefully examined, and we found the very same things which had a short time be- fore been collected at the surface with the tow-net and the scoop-net: nothing different was collected by the cylinder. The Radiolarians (two genera) were perhaps more numerous than at the surface.