PULMONATA. 65 



sharp keel ; the under side is tumidly convex, rising with a regular swell until it 

 approaches the umbilicus, into which it sinks rather suddenly, presenting a blunt 

 angle which defines the umbilicus. In the smaller of the two specimens, the spire 

 is more elevated, and the underside of the body-whorl more convex than in the 

 other. The umbilicus is deep and moderately wide ; the aperture transverse, and 

 wider than long. The specimen figured exhibits the impression of a slightly reflected 

 peristome. 



The present species is much less than the recent H. lapicida, the umbilicus is 

 smaller in proportion, the keel round the whorls more prominent, and, judging from 

 the cast figured, which appears to be that of a fully-grown shell, the aperture at 

 maturity does not present the downward inflection which characterises H. lapicida. 

 The condition of the keel is apparently a character of little value, inasmuch as it 

 varies considerably in specimens of H. lapicida, some of which, particularly in the 

 young state, have it as acute and prominent as that of the present shell. 



The smaller size of the umbilicus, and the absence of the downward inflection of 

 the aperture, are the most important differences ; but these characters, even if constant, 

 would scarcely justify my considering the shell as more than a variety. With only 

 two specimens, however, and those casts, I do not venture to pronounce as to their 

 identity with the recent species. If, on more perfect specimens being obtained, it 

 should appear that the shell presents the granulated surface which characterises 

 H. lapicida, I should feel little hesitation in referring it to that species. 



The specimen figured belongs to Mr. D'Urban's collection. 



Size. — Diameter, ^ an inch ; elevation rather more than 2-10ths in. 



Locality. — Headon Hill, where, however, it is extremely rare. 



No. 19. Helix omphalus. F. F. Edwards. Tab. X, fig. 5 a — e. 



Helix stmatella. £. Wood. Lond. Geol. Journ., vol. i, p. 118. 



H. testa planorbulari, dcpressd, undato-costidato-lineatd, umbilicatd: anfractibus 

 quaternis, conveziusculis ; suturis conspicuis, depressis : aperturd rotundato-semi-lunari ; 

 marginibus simplicibus ; wnbilico magno. 



This shell, which belongs to the section represented by Zonites, Montfort,* 



* The genus Zonites, as defined by Mr. Gray, embraces those Helices which have a depressed spire and 

 a lunate mouth, -with thin simple lips. It is divided into two sections — Verticillatee (Fer.), in which the 

 shell is brown, or varied, and striated ; and Hyalince (Fer.), in which the shell is hyaline, greenish or pale 

 brown, and polished. It appears, from the observations of Mr. W. Thompson, to which I have before 

 referred, that, judging from the characters afforded by the dentition, the animal of Z. radiatus (one of the 

 Verticillatee) is a true Helix; but that in four species of the Hyalince examined by him, the animals would 

 form a connecting link between Vitrina and the true Helices. Professor E. Forbes and Mr. Hauley, in 

 their ' History of British Mollusca,' restrict the genus to the Hyaline species. 



•9 



