118 EOCENE MOLLUSCA. 
which at once separates it from the preceding species; the casts, m which state 
specimens are most commonly found, may be distinguished by the more elevated spire, 
the less effuse base, and the narrower umbilicus. 
Size-—Axis, half an inch; diameter, nearly the same. 
Locality.—Sconce, where, although it is not by any means rare, it is not so common 
as C. cinctus. 
Genus 19th. CraspEDOPOMA.* Pfeiffer. 
CrasPpepopoma, Pfeiff., 1847. 
Vatyata (sp.), Menke. 
Boranta, Gray, 1842. 
Gen. Char.—Shell sub-turbinate ; last whorl slightly produced, straight, attenuated 
towards the aperture, which is circular; peristome continuous, simple, slightly 
thickened; axis imperforate or narrowly umbilicate. 
This is one of the genera, separated by Pfeiffer, (Zeitsch. fiir Malak.,) depending 
principally on the characters presented by the operculum. That appendage in the 
present genus differs from the operculum of Cyclotus,in bemg horny instead of cal- 
careous ; and in having, on the outer edge of the internal disc, a circular prominence 
which overlaps the margin of the aperture; the external disc is also flat, and not 
concave, as in Cyclotus. The shell is distinguished by the attenuation of the last whorl, 
which gives a contracted appearance to the aperture, a character not found in any other 
group of the Cyclostomide. Only two living species are known; both are from 
Madeira. 
No. 69. CRASPEDOPOMA ExizaseTum. F. £. Edwards. Tab. XIV, fig. 14a—c. 
C. testd parvd, conicd, perforata ; lineis spiralibus, numerosis, tenuissimis, ornatd; 
apice obtusiusculo: anfractibus quinis, rotundatis, ultimo decurrenti: aperturd circulari, 
intus incrassatd ; umbilico angusto. 
A small trochiform shell, ornamented with numerous fine, spiral, raised lines, and 
formed of four or five rounded volutions, the last of which is attenuated towards the 
aperture and slightly decurrent; the spire is moderately elevated, with a somewhat 
blunt apex: the aperture is nearly circular, and slightly thickened internally; the 
umbilicus is narrow. 
Without the assistance to be derived from the operculum, it is scarcely possible to 
determine correctly to what genus the present shell should be referred. It has much 
the appearance of a Valvata; but the thickened peristome indicates its affinity to the 
* Etym., xpaoredor, a rim or border; twpa, a lid, (the operculum.) 
