MUSEUM OF COMPARATIVE ZOOLOGY. 263 



the back with a space either side, then four or five similar ridges, parallel, 

 close-set, and becoming obsolete as the tube begins to be erect. Between the 

 longitudinal ridges are, in fine, specimens, fine elevated transverse lirse. The 

 sculpture is very variable in strength and often more or less obsolete. When 

 the tube begins to rise vertically it loses all its sculpture except irregular incre- 

 mental lines, and its calibre perceptibly diminishes. The color is yellowish or 

 grayish white. The height of the erect part is usually about an inch, and the 

 diameter of the aperture 1.75 mm. The greatest diameter of the same tube 

 (distortions apart) would be about 2.0 mm. 



Internally, very near the apex, are two laminae. The right one is large, 

 arched over with a thickened edge, the left one lower, thinner, and over- 

 shadowed by the other. Both are subtransparent, with opatpue whitish streaks. 

 These laminae are however very irregular; they seem to be altogether absent 

 in some individuals, and are perhaps sexual. They are obsolete or nearly so 

 in most specimens, and I have had to break many before finding a single per- 

 fect example of these appendages. The animal is soft and whitish. I could 

 see no eyes or tentacles. The operculum was translucent, spiral, as large as 

 the aperture, with a smooth flexible edge, the outside concave and polished. 

 Owing to the fact that the last whorl of the operculum seems to cover up the 

 others with its inner edge except toward the centre, it is difficult to ascertain 

 the number of turns. Very few of the numerous specimens contained the 

 animals, many were occupied by parasitic sipunculoids, chaetopods of several 

 species, and even Crustacea. 



This species is usually nearly solitary, or but few individuals are associated 

 in the clusters obtained by the Blake. 



Habitat. The Antilles, at Stations 2, 11, 32, 45, 139, 206, 208, 220, 247, 

 290, and 300, in 37 to 805 fins., on small solid objects, bottom temperature 

 from 40° to 71° F. 



The species has not been found northward on the coast of the United 

 States. 



Genus BIVONIA Gray. 



This group is characterized, according to Tryon and other authors, by a 

 rudimentary operculum, an interior free from laminae, and a dorsal carina on 

 the shell. It much resembles the cases of some Annulosa, from which it is 

 distinguishable by its less calcareous more porcellanous shell, and usually by 

 its larger size. 



In the absence of the soft parts, and with the nucleus lost from the speci- 

 mens in hand, I refer the following species to this group with some uncer- 

 tainty, and chiefly on account of the shell structure, which is certainly more 

 like that of Vermetus than any of the worm-shells known to me. 



