216 PNEUMONOBRANCHIATA. 



five plaits, two of which are much longer than the 

 rest. 



Ferussac, in his list of British Shells (Journ. Phys. 

 1820. 301.), says this shell has no analogy with any of 

 Draparnaud's; and Mr. Alder observes that it is dis- 

 tinct from Clausilia plicatula Drap., to which it has 

 been referred. 



The species was first discovered by Mr. Rolph in 

 Charlton Wood, Kent. It was first indicated as Bri- 

 tish by Ferussac, and then by myself. I have since, 

 at two distant periods, found it in the same locality, 

 and I have seen specimens from Hastings, Sussex. 



Like other species, it is sometimes found transpa- 

 rent and colourless. Dr. Turton indicates three 

 varieties in the teething, but it is very variable in 

 this respect. 



81. 4. Clausilia dubia. Doubtful Close Shell, 

 (t. . f. 143.) Shell dark brown, rather ventri- 

 cose, with strong raised striae, rendered some- 

 what granular by a few spiral ridges on the lower 

 whorls ; whorls ten or twelve, a little rounded ; 

 aperture with two teeth on the pillar, the lower 

 one forked internally ; peristome whole, detached, 

 and reflexed. 



Clausilia dubia. Drap. ; Alder, Cat. Supp. 1. c. 3. 

 Mag. Zool. §• Bot. ii. 111. 



Clausilia rugosa, var. Alder, Cat 1. c. 32. 



similis. Gilbertson, MSS. B. M. ; not 



Fer. 



Inhab. rocks under moss — North of England. 



This shell is about 5-8ths of an inch long, and 

 l-8th broad. 



