68 LAURIA, SUBGENUS LEIOSTYLA. 



pean L. anglica. Others have no callus connecting angular 

 lamella and lip-insertion, thereby agreeing with the species of 

 the Azores and Canaries, and with the Transcaucasian L. 

 tenuimarginata. The Porto Santo species are closely related 

 to part of those of Madeira, but the hydrophilous Madeiran 

 groups have no representatives on the smaller, dryer island. 



Key to Species of Leiostyla. 



f Species of Western Europe, British Islands to Algeria 



| (2) 



1 ^ Species of the Caucasus and adjacent regions (4) 



{ Species of the Atlantic islands, Madeira, Azores and 

 (^ Canaries (12) 



Species of Western Europe, Britain to Algeria. 



- Base with a wide, deep umbilicus as in L. cylindracea; 

 surface with strong, regular stria? ; Portugal. 



L. paulinoi, no. 23 



- Base minutely perforate and openly rimate (3) 



Smoothish; angular lamella connected by a callus with 

 the lip insertion; British Is., Portugal. 

 3-1 L. anglica, no. 22 



Finely subcostulate ; angular lamella free from the lip 

 insertion ; Algeria. L. numidica, no. 24 



Species of the Caucasus and Adjacent Regions. 



r Columellar lamella forming a broad and steeply ascend- 

 j ing plate deep within (5) 



j Columellar lamella entering horizontally, ascending but 

 *> little deep within, its edge slanting downward (6) 



r Smoothish; about 5 or 6 mm. long; columellar lamella 

 J not emerging. L. caucasica, no. 15 



I Finely striate ; 3.2 to 3.5 mm. long ; one or two columel- 

 v lar lamellae emerging. L. pauUnce, no. 16 



f Surface smoothish (7) 



1 Surface distinctly ribbed or rib-striate (10) 



