V0 1889. 11 '] PROCEEDINGS OF THE NATIONAL MUSEUM. 307 



Pleurotomella argeta sp. nov. 

 Plate vi, Fig. 5. 



Shell polished, short-fusiform, snow white, eight- whorled; nucleus 

 eroded in the specimen; whorls full, oppressed in front of the suture, 

 elsewhere gently rounded; transverse sculpture of delicate incremental 

 lines; spiral sculpture of obscure almost microscopic striae and a few 

 close set extremely fine threads on the canal; aperture elongated ; anal 

 notch very shallow, rounded; leaving only a faint slightly flattened 

 fasciole; outer lip sharp, simple, arched well forward, especially ante- 

 riorly; body without callus; pillar thin, white, short, slightly twisted ; 

 canal short, very wide, hardly differentiated; maximum longitude of 

 shell 43; maximum latitude 20 Ium . 



Hab.— U. S. Fish Commission Station 2807, in 812 fathoms, mud, near 

 the Galapagos Islands; bottom temperature 38°.4 P. 



The characters of this species are as simple as possible, yet a more 

 elegant and delicate shell can hardly be imagined. 



The soft parts are yellowish brown and agree externally in all respects 

 with those of the preceding species. Like that, it was impossible to 

 extract them without wholly destroying the shell, as they had been 

 placed in alcohol so strong as to make them as hard and tough as sole- 

 leather. In most Pleurotomidw there is very little if any muzzle be- 

 tween the tentacles ; at least when the proboscis is wholly retracted the 

 inner bases of the tentacles, somewhat vertically flattened, are connate 

 at a shallow sinus iu the middle line. In the present and the preced- 

 ing species, however, the tentacles are widely separated and cylindrical, 

 and there is a muzzle which is longer than the tentacles, when both are 

 contracted in alcohol, into the center of which the proboscis is retracted 

 and which has a flattish end almost as in Litorina. Something of the 

 sort is found in Conus if the figures are to be believed. More investi- 

 gation in regard to this character is required. 



Pleurotomella (Gymnobela) agonia sp. nov. 

 Plate vi, Fig. 4. 



Shell small, thin, bright yellow-brown, with six full and rounded 

 whorls, the nucleus lost, but without doubt of the Sinusigera type; 

 spiral sculpture in front of the fasciole of numerous sharp elevated 

 threads with wider interspaces, between each pair of which, except on 

 the canal, are one or two smaller intercalary threads ; on the fasciole 

 there are only a few comparatively faint threads, which do not rise 

 above the transverse sculpture, while on the body the spiral sculpture 

 is predominant though minutely undulated by the other ; the transverse 

 sculpture is composed of numerous fine, rounded, somewhat elevated 

 threads with wider interspaces, forming a series of elegant concavely 

 arched ripples on the anal fasciole, beyond which they become fainter, 



