CYLICHNA. 299 



the middle, tapering toward the posterior end and broadly rounded 

 in front, so that the outline is somewhat conical, but truncated pos- 

 teriorly. At the tip there is a small, but rather deep pit. The 

 outer lip is thickened, and somewhat constricted below the middle 

 and then slightly expanded and broadly rounded anteriorly ; pos- 

 teriorly it bends inward and projects slightly beyond the tip of the 

 shell, and forms a distinct, rounded, posterior sinus. The colurnella 

 margin is thickened, without a fold, and moderately excurved. The 

 umbilicus is narrow but deep. The aperture, in front of the middle, 

 is moderately broad and ovate, but farther back it is much nar- 

 rowed and encroached upon by the body-whorl. The surface is 

 smooth and polished, without any sculpture except a few faint spiral 

 lines close to the posterior end and others which are wavy and even 

 less distinct at the anterior end. Color of the type-specimen, pure 

 white, with a very thin yellowish-white epidermis on some parts. 

 Length 6 mill. ; greatest breadth, 4 mill. ; length of aperture equal 

 to that of the shell ; its greatest breadth, 1-8 mill. ( F)- 



Station 2265, off Cape Hatteras, in 70 fathoms. 



Cylichna eburnea V., Tr. Conn. Acad. vi, p. 428, pi. 44, f. 14. 



This species is readily distinguished from all others of our coast 

 by its thickness and solidity, by its distinct umbilicus and by the 

 evident pit at the posterior end. In form it somewhat resembles 

 Diapliana conulus but it is less narrowed posteriorly, besides being a 

 much larger and stouter shell. (F.) 



C. DISCUS Watson. PI. 30, fig. 7. 



Shell narrowly cylindrical, truncated in front like Cylichna alba 

 (Brown), smooth, thin, polished, with a small disk-like minutely 

 perforated top. Sculpture : Longitudinals there are very faint 

 and slight lines of growth. Spirals there are some very doubtful 

 indications of a coarse spiral structure in the texture of the shell. 

 Colour milky-white and glossy. Mouth the full length of the shell 

 but not more, extremely narrow with lips nearly parallel till they 

 diverge in front, the inner lip following the slow basal contraction, 

 while the outer expands a very little, as is the case in Cylichna um- 

 bilicata (Mont.) ; at the upper end is a small narrow, but deepish 

 rounded sinus. Outer lip ; its edge is very straight, retreating a 

 little quickly above and slightly in front ; its direction is straight, 

 with the very slight bend to the right spoken of above. Top a little 

 contracted, rounded, with a sort of thickened pellucid disk which is 



