DESCRIPTION OF SHELLS. 181 
Turritella conoidea. (Tab. V. figs. 6 & 10.) 
This species is so variable that the synonyms cannot be satisfactorily given. 
Turritella contracta. (Tab. VII. fig. 42.) 
Spec. Cuar.—Turrited, elongated, nearly smooth, or obscurely granoso- 
striate; whorls concave, their lower edges very prominent, rounded, marked with 
two or three obscure ridges. 
Very nearly resembling some varieties of T. conoidea, but its whorls are more 
concave and nearly smooth, and their upper edges are not rounded into the 
suture. 
Turritella marginata. (Tab. VI. fig. 16.) 
Spec. Cuar.—Conical, elongated, with convex whorls; ornamented with 
about nine sharp transverse ridges upon each whorl, a small portion of the upper 
part of which is plane. 
Length little more than twice the width. 
The convex whorls and smooth band around the upper part of each distinguish 
this shell. 
Turritella nexilis. (Tab. VI. fig. 17.) 
Spec. Cuar.—Conical, elongated, with flat whorls, of which the lower edge 
is rather prominent ; covered with sharp transverse ridges, which are numerous 
and only slightly raised. 
Length two and a half times the breadth. 
A very neat shell. There are ten or twelve unequal ridges on each whorl. 
The small specimen is in Mr. Edwards’s Cabinet. 
The five latter species of Turritelle in this List belong to one group of the 
genus, and the four preceding to another, in both of which the species are very 
difficult to define, because there are so many intermediate forms. Turritella 
intermedia, Desh., is also in Mr. Edwards’s Cabinet of Bracklesham Bay fossils. 
Cerithium incomptum. (Tab. VI. fig. 18.) 
Spec. Cuar.—Turrited, with straight sides; the upper half of each whorl 
28 
