GASTERUPODA. HELICID. 87 
belongs to another division. The colour of the shell, in a fine 
state, is deep-red fuscous, or intensely chocolate-brown ; the 
peritreme and lamellze white. 
This species is found alive in the environs of London, beneath 
the bark of old willows, and is thrown up amongst the rejecta- 
menta of the Thames in great profusion, especially after floods. 
It was first discovered to inhabit Britain by. Montagu, who took 
it at Easton Gray, in Wiltshire. 
4. CLAUSILIA RUGOSA. 
C. testa fusiformi, gracili, subpellucida ; anfractibus transver- 
sim crebro elevato-striatis ; apertura trilamellata: lamella 1 
postica; 1 dextra; altera abbreviata, antic. 
Turbo bidens, Penn. Brit. Zool. iv. 131; Mont. Test. Brit. 
ge. tA. fig. 7. 
Clausilia rugosa, Drap. Hist. des Moll. 73. 
Turbo nigricans, M. §& R. Trans. Linn. Soc. viii. 180; Dill. 
Desc. Cat. 875. 
Odostomia nigricans, Plem. Edinb. Encycl. vii. 76. 
Animal nigrum aut nigricans. Operculum anticé subacumi- 
nato-rotundatum. 
Habitat in muscosis, passim. 
Shell club-shaped, slender, somewhat pellucid; the whorls 
with thickly-set elevated strize ; aperture with three lamellee ; 
one behind, one on the right; the third shortened, anterior. 
Height nearly half an inch. 
Colour chocolate-brown, or deep fuscous, tinged with red. 
Peritreme whitish, or slightly tinted with reddish. 
Animal pale or dark sooty-black. Operculum anteriorly 
slightly acuminated, and rounded. 
Clausilia rugosa is found in every part of Britain in great 
plenty. It resides generally under moss. 
I have received from the Provost of Eton a Clausilia, with 
an imperfectly formed aperture, having the general habit of C. 
rugosa, from which it differs, in being more elegant and slender 
in form, and in wanting the elevated stric, excepting at the 
extremity of the last whorl, where they are very evident. It has 
much the air of the Swiss C. parvula, of Studor, which is very 
