NARRATIVE OF THE CRUISE. 169 



than -2400 fathoms contained less, and those from depths less than 2400 fathoms 

 contained more, than 50 per cent, of carbonate of lime, the highest percentage being 

 88'30 in 1675 fathoms. In the greatest depths, 2850 and 2875 fathoms, there were 

 only 8 and 10 per cent. In the greater depths the lime consisted chiefly of fragments 

 of pelagic Foraminifera and Coccoliths ; in depths less than 1600 fathoms, the shells of 

 pelagic Molluscs and fragments of Echinoderms were more or less abundant, and along 

 with pelagic and other Foraminifera made up the principal part of the carbonate of 

 lime in the deposits. Radiolarians and Sponge spicules sometimes made up 3 or 4 per 

 cent, of the deposit. 



In the deep water, immediately to the south of the banks of Newfoundland, there were 

 fragments of quartz, monoclinic and triclinic felspars, and fragments of mica-schist and 

 other ancient continental rocks. These were believed to be ice-borne fragments, although 

 apparently south of the southern limit of the ice region in the North Atlantic as shown on 

 the charts. On approaching the Azores these fragments disappeared completely from the 

 bottom, and the mineral fragments then consisted almost entirely of volcanic minerals 

 and pumice. Except the pumice, the mineral particles seldom exceeded 0"25 mm. in 

 diameter, and generally they were much smaller. A few fragments of tufa coated with 

 peroxide of manganese were dredged. 



Boats were several times lowered for the use of the Naturalists. On the 26th a small 

 Hawksbill Turtle (Eretmochelys imbricata) covered with barnacles and small crabs, was 

 captured ; its stomach was filled with Vellelas. A large box was observed, a few days 

 later, and on being hoisted on board, was found to contain decaying salt' meat. It was 

 covered with Barnacles (Lej>as anatifera) and surrounded by fish, the attempts to 

 capture which were unsuccessful. Very little Gulf Weed was met with during the passage 

 but some pieces of Fucus vesiculosus were picked up, to which were attached several 

 specimens of Scyllcea pelagica. Nairtilograpsus minutus was observed resting on every 

 floating thing ; many were found on Ianthina shells, and it was curious to observe that 

 several of them had a distinctly blue tinge in imitation of the colour of these shells. 

 Dr. v. Willemoes Suhm writes in his journal : — " Nautilograpsus minutus, the small crab 

 found in all the oceans clinging to gulf weed, logs, or animals larger than itself, was obtained 

 to-day (21st) resting on Ianthina. Closer examination showed that it was covered with 

 small brown spots, which proved to be little parasitic Nemertines. This is the first known 

 example of a Nemertine living as a parasite. The worm, a small ordinary Tremacephalid, 

 presents no modification induced by parasitism; it appears to be a new species, and from 

 its colour may be called Tetrastemma fuscum. In accordance with the character of 

 the genus, it has two large eyes, and two very small ones, one on each side of the pro- 

 boscis. The ganglia are especially large and conspicuous, and send out two nervous 

 branches running along the sides of the body. The proboscis is very short, and 

 distinguished from all other species I know of by having the stylet-sac placed close 



(NAUR. CHALL. EXP. — vol. i. — 1884.) 22 



