186 DESCRIPTION OF SHELLS. 
Very rare. A distinct and remarkable shell ; the specimen is much crushed, 
which makes it appear wider than it really is. It is one of Mr. Edwards’s 
treasures from the yellow sand beds. 
Fusus leviusculus. (Tab. VII. fig. 34.) 
Serc. Cuar.—Elongated, with nearly straight sides, transversely striated ; 
whorls slightly concave towards their upper margins; strie rather distant ; 
aperture wide, with a small narrow canal above, and a short narrow beak ; outer 
lip striated within. 
Length 5, width 2; aperture and beak equal to the width. 
Remarkable for the short aperture and proportionally long spire. 
Strepsidura armata. (Tab. VII. fig. 11.) 
Spec. Cuar.—Ovate, pointed, short; whorls striated above, each armed with 
about eight pointed tubercles, smooth below ; aperture ovate, narrow above ; 
base striated ; beak curved. 
Length, including the beak, about twice the width. 
A shell with a smooth aspect ; it can hardly be called ribbed, the tubercles are 
so little extended at the base down the whorl, which is in part free from striz 
and somewhat flattened ; it differs from Strepsidura turgida in the form of the 
aperture. We have not seen the beak perfect. 
The genus Strepsidura was proposed by Swainson, and is well distinguished 
from Fusus by the curved beak as well as the short form. 
Triton expansus. (Tab. V. fig. 15.) 
Spec. Cuar.—Subfusiform, costated, crossed by numerous linear ridges, some 
of which are so thickened as they pass over the costz and varices as to produce 
three or four tubercles, the uppermost of which are spiniform ; aperture obovate ; 
beak narrow, slightly recurved. 
Length, including the beak, nearly twice the width. 
Coste three or four between each varix ; the two upper tubercles of each row 
generally remain visible upon the spire, but not constantly; the uppermost is 
always the most prominent. The narrow beak is equal in length to the 
aperture. 
