Mollusca of Great Britain. 351 



instances of this seeming disorganization are still more 

 numerous, while our researches become necessarily more 

 confined ; and we are at last forced to confess how very 

 imperfect our greatest diligence has been, and what a 

 large extent of ground yet remains untrodden in the fields 

 of natural history. 



* Incompleta ; umbilico perforata. 



1. Fragilis. 



Animal flavo-fuscescens. Ten taenia superior a breviora, cla- 

 vata. 



Testa clavata, subventricosa, striata, pellucida, nitida, fulva. 



Anfractus 6 — 7. Apertura compressa, subquadrata, 



interdiim uniplicata : peristomio simplici, postic6 sub- 



reflexo. 



Long. 0.25.— Diam. 0.085. 



Turbo perversus. Linn. Syst. Nat. 1. p. 1240. 

 Pupa fragilis. Drap. Hist, des Moll. p. 68. t. 4<.f. 4. 

 Balea fragilis. Leach Mss. 



Among moss, under the bark of trees, &c., but not very 

 common. The females have their shells much more ven- 

 tricose and with fewer volutions. 



** Completa ; umbilico imperforato. 



2. Nigricans. 



Animal nitidum, fuscum, supern^ corrugatum. Sustenta- 

 culum tenuius, angustum. 



Testa subventricosa, subopaca, subcrenato-striata, nigres- 

 centi-fusca. Anfractus 10 — 12. Apertura subtrian- 

 gularis plicis 2 columellaribus distantibus instructa: 

 peristomio producto, albido, incrassato. 



Long. 0.5.— Diam. 0.085. 

 VOL. XVI. 2 z ClausiKa 



