180 DESCRIPTION OF SHELLS. 
Adeorbis planorbularis. (Tab. IX. fig. 20.) 
A neat little shell found by Mr. Edwards. 
Orbis patellatus. (Tab. IX. fig. 23.) 
A curious shell and precisely corresponding with the French specimens. I 
quote Lea with a note of doubt, because, although his figure and description 
agree with this shell in almost everything, the size (0°15 of an inch) is so very 
different, that it is hardly possible they can be the same species: the American 
shell is almost microscopic; it is the type of the genus Orbis. Another of 
Mr. Edwards’s discoveries. The specimen found in the Isle of Wight is in 
Mr. Morris’s Cabinet. 
Bifrontia. 
We are indebted to Mr. Edwards’s minute researches and delicate handling for 
all the species of this genus ; they are remarkably typical of the French beds as 
distinguished from the clays of Barton and London, and indicate the relationship 
of the Bracklesham sands. They are all extremely tender shells. 
Rotella minuta. (Tab. IX. fig. 19.) 
Spec. Cuar.—Convex, smooth and shining; margin slightly angular ; aper- 
ture semioval, oblique ; base rather convex, the central callus small, defined. 
This species of a genus rarely found fossil can only be compared with Rotella 
nana of Lea, ‘ Contrib. to Geol.’ p. 214, t. 6. f. 225, which is a thicker and 
squarer shell, also rather less. 
Mr. Edwards’s Cabinet. 
Turbo plicatus. 
Mr. Edwards has this shell in his Cabinet. 
Turritella bicincta. (Tab. VI. fig. 19.) 
Spec. Cuar.—Turrited, elongated; covered with granose threads; whorls 
rather concave, their lower edges prominent, bicarinated; aperture..... 
This resembles T. conoidea, but is easily known by the two spiral ridges along 
the lower edges of the whorls. 
