EEPORT ON THE ANNELIDA. 
441 
covered by a large flap in front of the mouth. The latter is borne upon a proportionally 
larger buccal process than in the Norwegian form. Just behind the anterior margin of 
the snout, in front of the branchiae, are two long and somewhat crescentic bands of 
pigment-specks. These are probably rudimentary eyes. 
The branchiae correspond with the typical arrangement. No dorsal hooks are visible 
behind these, and since four examples are in this condition, it is possible they are absent 
in this species. The denticulations on the dorsal edge of the fourth segment are more 
filiform than in Melinna cristata. 
The bristles agree in arrangement and a23pearance with those of the latter species, but 
microscopically present greater tenuity at the extremities, which form very fine, slender 
processes. On the prominent ridge on each side of the fimbriated row is a dense group 
of simple bristles, and two similar tufts in front of it, as in Melinna cristata. 
The hooks (PI. XXVIIa. fig. 17) somewhat resemble those of Melinna cristata, from 
Norway, and, indeed, it would be difficult to point out any single feature that would be 
wholly diagnostic. The basal region in the new form, however, is decidedly more 
massive. A minute comparison also reveals that the curve below the third or great 
tooth, and that below the fourth or accessory fang, differ from those in Melinna cristata, 
the former curve being smaller, the latter larger in the abyssal form. The posterior 
hooks do not differ to any material extent. 
The greyish mud in the alimentary canal contained numerous Diatoms, often like the 
other organisms coated with the very fine mud, rounded, trilobate, and other Eadiolarians, 
fragments of arenaceous Foraminifera, and broken sponge-spicules, including a remark- 
able form possessing lateral processes with divided extremities. 
The tube is composed of an exterior investment of very fine greyish-brown mud lined 
by the usual chitinous secretion. It is rather friable. One end is enlarged and appar- 
ently almost closed, a deposit of semifluid mud generally being found internally. The 
diameter of the tube varies from 5 to 7 mm. Microscopically the same structures occur 
in the very fine mud of the tubes as in the food, with the exception that the Foraminifera 
here and there are larger, and that on the whole the field is less rich in organisms. The 
Eadiolarians are enveloped in an investment of mud, which is so fine that the slightest 
movement of the tube in the spirit causes opacity. 
MelinnoiJsis, n. gen. 
Melinnopsis atlantica, n. sp. (PI. XXVIIa. fig. 18). 
Habitat. — Dredged at Station 44 (off Chesapeake Bay, North America), May 2, 1873 ; 
lat. 37° 25' N., long. 71° 40' W.; depth, 1700 fathoms; bottom temperature 36°'2, 
surface temperature 56°‘5 ; sea-bottom, blue mud. 
(ZOOL. CHALL. EXP. — PART XXXIV. 1885.) 
LI 56 
