118 EOCENE MOLLUSC A. 



which at once separates it from the preceding species ; the casts, in 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. ductus. 



Genus 19th. Craspedopoma.* Pfeiffer. 



Craspedopoma, Pfeiff., 184/. 

 Valvata (sp.), Menke. 

 Bolania, 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. fur Malak.,) depending 

 principally on the characters presented by the operculum. That appendage in the 

 present genus differs from the operculum of Cyclotus, in being 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 fiat, 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 Cyclostomida. Only two living species are known ; both are from 

 Madeira. 



No. 69. Craspedopoma Elizabeths. F. E.Edwards. Tab. XIV, fig. 14 a — c. 



C. testa parvd, conicd, perforata ; lineis spiralibus, numerosis, temiissimis, ornatd; 

 apice obtusiusculo : anfractibus quints, 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., Kpdoitebor, a rim or border; ir^fia, a lid, (the operculum.) 



