PULMONATA. 117 



and numerous genera and sub-genera have, in consequence, been withdrawn by Gray, 

 Guilding, Troschel, Pfeiffer, and others, on characters taken principally from modifi- 

 cations of the operculum. The present genus was separated by Mr. Guilding, from 

 Cyclophorus, for some shells from the West Indies ; it is distinguished by the thick 

 calcareous operculum, formed of two distinct layers. The animal, so far as it is 

 known, resembles that of Cijclostoma. 



The recent species are not very numerous. Mr. Gray, in his Nomenclature of 

 Molluscous Animals, &c, in the British Museum, part " Cyclophoridse," gives a list of 

 twenty-eight species, all of which are from the West Indian Islands, or from Central 

 or South America. 



No. 67. Cyclotus cinctus. F. E. Edwards. Tab. X, fig. 1 a — c. 



C. testa conico-depressd, linen tenuibus spiraliter cinctd; anfractibus quinque vel sex, 

 rotundatis, ultimo paullo decurrenti : umbilico magno; aperturd sub-circulari. 



This remarkably elegant shell is conical and somewhat depressed, formed of five or 

 six rounded whorls, and ornamented with numerous, irregular, rather sharp, spiral, 

 raised lines, some of which are more elevated than the rest ; these lines are spread 

 over the whole surface Of the shell ; but they are more crowded on the upper than on 

 the under surface, and are very prominent in the umbilicus, where they are sometimes 

 strongly decussated by the lines of growth. The last whorl is slightly decurrent; the 

 aperture is nearly round, with the peristome a little reflected, but not much so; and 

 the umbilicus is very wide, being nearly one third of the diameter of the shell. 



Two or three detached opercula have been obtained by Mr. D'Urban, which present 

 all the leading characters of the opercula of the living species ; but, as yet, it cannot 

 be determined to which of the two fossil species they belong. They are thick, 

 testaceous, slightly concave externally, formed of five or six slowly enlarging whorls 

 with the external fringe deeply grooved. One of them is represented by fig. 12 a — b, 

 Tab. X. 



This species has hitherto been found only at Sconce, where it occurs rather plenti- 

 fully; but specimens with the shell preserved are rare. 



Size. — Axis, 5-10ths of an inch; diameter, rather more than 6-10ths of an inch. 



No. 68. Cyclotus nudus. F. E. Edivards. Tab. X, fig. 11 a — b. 



C. testa ovato-conicd, lavi; spird mediocri; anfractibus quinis convexis-. aperturd 

 rotundatd, umbilico parvo. 



A smooth ovately-conical shell, with a moderately elevated spire, formed of five 

 convex volutions : aperture nearly circular; umbilicus narrow but deep. 



The surface of the shell in this species is perfectly devoid of ornament, a character 



