MADEIRAN GROUP. 281 



Canarian ones of the T. Lowei in being altogether a trifle 

 smaller and narrower ; but I have no means of judging whether 

 it is a normal one of its race. 



Fam. 3. ASSIMINEID^E. 



Grenus 3. ASSIMINEA, Leach. 

 Assiminea littorina, 



Helix littorina, Del. Chiaje, Mem,. An. Nap. iii. 215. 

 Assiminia littorea, Paiva, Mon Moll. Mad. 163 (1867) 

 Assiminea littorina, Watson, Journ. des Conch. 220 (1876) 



Habitat Maderam ; sub lapidibus sestu maris quotidie sub- 

 mersis, hinc inde congregans. 



This very diminutive Assiminea, which occurs also in more 

 northern latitudes, and which is easily recognizable by its com- 

 pact, globose-ovate, Paludina-like form, its solid substance, 

 almost unsculptured surface, pallid hue, and perfectly edentate 

 aperture, is locally abundant on the shores of Madeira proper, 

 where it was first detected by the Eev. E. B. Watson in 1865. 

 And it has been obtained also by the Baron Paiva from the 

 Great Salvage. 



Fam. 4. HYDROBIIDJE. 



Genus 4. HYDROBIA, Hartm. 



Hydrobia similis. 



Cyclostoma simile, Drap., Hist. Nat. 34. pi. 1. f. 15 (1805) 

 Rissoa anatina, Forb. et Hani., Hist. Brit. Moll. iii. 134 

 Hydrobia similis, Jeffr., Brit. Conch, i. 64 



Paiva, Mon. Moll. Mad. 161 (1867) 



Watson, Journ. de Conch. 224 (1876) 



Habitat Maderam ; in aquis quietis circa Funchal hinc inde 

 vulgaris. 



The European H. similis (which I found also at Mogador 

 on the opposide coast of Morocco) occurs abundantly in the 

 rivers and tanks of Madeira proper, where it was detected in 

 1865 by the Rev. R. B. Watson, and where I have myself sub- 

 sequently met with it (near Funchal) in considerable profusion. 

 It bears at first sight so strong a resemblance to the Limnwa 

 truncatula that, before accurately examined, it might almost 

 be mistaken for that species ; nevertheless, apart from its modus 

 vivendi, which appears to be as much in brackish water as in 

 fresh, and the fact of its possessing an operculum, it will be 



