92 GASTEROPODA. HELICID. 
Britain. It is not the P. Muscorum of the various continental 
writers, quoted by British conchologists. 
Animal cinereous, grey, or very pale fuscous. 
2. PuPILLA MARGINATA. 
P. apertura posticé lamella parva, centrali instructa. 
Pupa marginata, Drap. Hist. Nat. des Moll. 61. pl. 3. figs. 36- 
37. 
Turbo chrysalis, Turt. Conch. Dict. 220. 
Animal nigricante-griseum ; tentacula subtus pallida; pes oli- 
vaceus aut griseus. | 
Habitat sub lapidibus et muscis. 
Aperture of the shell behind, with a little lamella in the 
middle. Height three-sixteenths of an inch. Colour chocolate, 
or ferruginous-brown, somewhat pellucid. Peritreme tinted 
with reddish. Lamella white. Whorls slightly striated trans- 
versely, and somewhat glossy. 
This species is found alive near Hertford and Norwich. It 
is very common amongst the rejectamenta of the Thames, be- 
tween Eton and London; and likewise occurs amongst the re- 
jectamenta of the river Exe, in Devon. 
Animal blackish-grey ; tentacula pale beneath ; foot oliva- 
ceous, or grey. 
Genus 40. VERTIGO. 
Vertigo, Miiller. 
Testa obtusé-turrita ; ad apicem subgradatim obtusa. Aper- 
tura subpyriformis, ad dextram impresso-angulata. Peritrema 
marginatum, reflexum, interné fortiter inchoatum, rectum. 
Umbilicus perforatus. Tentacula superiora mediocria, ad api- 
cem paululum dilatata: inferiora brevissima, obsoleta. 
Shell obtusely turrited, its apex very obtuse. Aperture some- 
what pear-shaped, with an impressed sinus on its right side. 
Peritreme margined and reflexed, internally strongly commenced 
and straight. Umbilicus perforate. Upper tentacula mode- 
rate, slightly dilated at their extremities: under ones extremely 
short, obsolete. 
