84 



fresh water shells it possesses the power of gliding along the siu- 

 face of the water, with the shell downward. 



This shell is something like T. reticulata, but the sculpture is 

 less profound, and it has never any appearance of varices, or in- 

 crassation of the labrum. 



TuRRiTELLA IMPRESSA. — Shell dusky, acute at the apex ; volu- 

 tions six, with about four acute, impressed, revolving lines ; labrum 

 not thickened, a slight indentation at its base, and a projecting 

 angle within its middle. 



Inhabits the coast of Maryland. Length more than one-eighth 

 of an inch. 



I have seen but two specimens of this species. The aperture 

 is precisely similar to that of the preceding species. 



TuRRiTELLA BISUTURALIS. — Shell thin, pellucid, small, conic ; 

 whirls five, wrinkles almost obsolete, a revolving impressed line 

 near the suture ; suture not deeply impressed ; spire gradually 

 tapering, rather longer than the aperture; aperture rounded at 

 base, and perfectly entire. 



Length rather more than one-tenth of an inch. Inhabits Boston 

 harbor. My cabinet. 



I am indebted to Mr. Aaron Stone for this small species of 

 Turritella. It is distinguished from all others that I have seen, 

 by the single impressed line, which revolves near the suture. 



Bulla solitaria. — Shell remarkably thin and fragile, pellu- 

 cid, oval, narrowed at base, with numerous impressed revolving 

 lines, and transverse very obtuse wrinkles ; aperture surpassing the 

 tip of the shell ; spire none, substituted by an umbilicus ; umbilicus 

 of the base none. 



Less than half an inch. Inhabits the southern coast of the 

 United States. 



I found a specimen of this species of Bulla on the coast of 

 Maryland, but have not seen another. It is probable that it is 

 rare. It approximates to the description of B. hydatu, but it can 

 hardly be the same, as it is more oblong than the species B. 

 naucum agreeably to the figure in the Encyc. Meth., which spe- 

 cies is referred to by Dillwyn, as being of the same form with 

 hydatis. 



Melampus bidentatus. — Shell thin, fragile, dirty-brownish ; 



