PULMONATA. 115 



behind. The mode of progression, as described by Adanson, is as follows : the 

 animal, having attached itself by the posterior lobe, protrudes the anterior lobe as far 

 as the hollow part of the foot, which is capable of considerable extension, will permit ; 

 and the posterior lobe is then advanced until it touches the anterior one. This move- 

 ment, quickly repeated, enables the animal to advance with a rapidity apparently dis- 

 proportioned to its size. Adanson states that, on the animal emerging from or with- 

 drawing into the shell, the lobes pass one on each side of the large posterior fold, 

 which, being continued into the interior of the shell, keeps them constantly 

 separated. 



Only three or four living species are known, all from tropical regions. Of fossil 

 species, M. D'Orbigny, in his ' Prodrome de Paleontologie,' cites five, which he refers 

 to this genus, from the Eocene formations in France. 



No. 66. Pedipes glaber. F. E. Edwards. Tab. X, fig. 9 a — c. 



F. testa minutd, ovali, ventricosd, glabra; anfractibus quaternis vel quints, ad suturam 

 adpressis; spird mediocri: aperturd semiovali; labro uniplicato, antice intus incrassato; 

 plica columellari posteriori, angulatd, jlexd. 



A minute, oval, ventricose and smooth shell ; volutions four or five, adpressed at the 

 posterior margins so as to form a narrow band round the suture; the spire moderately 

 elevated : the aperture semioval; the outer lip with a sharp edge, and furnished with 

 a fold placed about the middle, and in front of which the lip is thickened internally; 

 the large columellar fold on the penultimate whorl is angulated and bent so as to present 

 a slight concavity on the anterior surface, and a corresponding convexity on the 

 posterior one. 



This exceedingly rare and interesting shell forms part of Mr. D'Urban's valuable 

 collection. 



Size. — Axis, 2-20ths of an inch nearly; diameter, rather more than l-20th. 



Locality. — High Cliff. 



Svh-Orvek—PHANEROPNEUMONA (Gray), OPERCULATA, (Ferussac.) 



Family — CyclostomidjE. 



Genus 18th. Cyclotus.* Guilding. 



Cyclotus, Guild., 1840, (fide Swainson.) 

 Poteria, Gray, 18-40. 

 Aperostoma, Troschel, Pfeiffer, 1847- 

 Cyclotus, Gray, 1850. 



* Etym., kvkXwtos, rounded. 



