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. 
* Incomplete ; umbilico perforato. 
1. FRaAGILIs. 
Animal flavo-fuscescens. Tentacula superiora breviora, cla- 
vata. 
Testa clavata, subventricosa, striata, pellucida, nitida, fulva. 
Anfractus 6—7. Apertura compressa, subquadrata, 
interdàm uniplicata : peristomio simplici, posticé 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. 
** Complete ; umbilico imperforato. 
2. NIGRICANS. 
Animal nitidum, fuscum, superné corru gatu PAMeMo- 
culum tenuius, angustum. —— ex MS 
Testa subventricosa, subopaca, bodie dins, nigres- 
 centi-fusca. Anfractus 10—12. Apertura subtrian- 
gularis plicis 2 columellaribus distantibus instructa : 
peristomio producto, albido, incrassato. 
Long. 0.5.— Diam. 0.085. ad 
VOL. XVI. 2 z . . Clausilia 
