490 TESTACEA ATLANTIC A. 



the Helix ad/vena, Bulhnus gemmula, Stenogyra Goodallii and 

 siilxliaphana, and Pupa acarus and gorgonica, having all the 

 appearance, as it seemed to me, of being well-nigh universal. 

 Still, this may have been more apparent, perhaps, than real ; 

 for the very limited number of the forms which came beneath 

 our notice precluded any safe inferences on the general subject 

 of local distribution. 



With only 41 exponents from which to judge, it is scarcely 

 possible to build up any very trustworthy theory on the affinities 

 of the Pulmonobranchiata of the Cape-Verdes ; and yet even 

 the fragmentary catalogue which has hitherto been brought to 

 light reveals a certain amount of evidence which points un- 

 equivocally, as I cannot but think, to their connection with 

 those of the Madeiran Group. In venturing on this opinion, 

 however, I would lay little or no stress upon the presence of a 

 few forms — such as the Helix armillata and lenticula, the 

 Bulimus ventricosus, the Stenogyra decollata, and the Acha- 

 tina lubrica — which there is every reason to suspect may have 

 been accidentally introduced through indirect human agencies, 

 and which abound, to a greater or less extent, in the more 

 northern archipelagos ; for those particular species belong to a 

 small assemblage which are eminently liable to transmission 

 (sometimes along with ballast in vessels, though more often in 

 consignments of plants), and the intercommunication between 

 Madeira and the Cape-Verdes (which are likewise Portuguese), 

 although perhaps never very considerable, would be more than 

 sufficient, during a period of two or three hundred years, to 

 account for the establishment of any or all of them in this more 

 southern cluster. But, putting these out of the question, as 

 possessing but a doubtful significance for the purposes of gene- 

 ralization, there still remains a conspicuous relationship be- 

 tween the most important Helices of the Group and those of 

 the erubescens and membranacea type which constitute so 

 marked a feature in the Madeiran fauna. This will be at once 

 apparent from the unmistakeable resemblance of the H. advena, 

 W. et B., to the state of the protean H. erubescens, Lowe (from 

 the east of Madeira proper, and from the Ilheo Chao), which 

 I have cited as the ' var. 7. advenoides ;' from the kinship (as 

 it were) of the H. Bollei, Alb., the H. leptostyla, Dhn., and the 

 H. serta. Alb., with other modifications of the erubescens ; 

 from that of the H. subroseotincta, Woll., with the Madeiran 

 H. membranacea, Lowe ; and perhaps also from even that of 

 the subfossil H. atlantidea, Morelet, with the (equally extinct) 

 H. chrysomela, Pfr., from Porto Santo; — all of which, and 

 others (from both archipelagos), are embraced by the particular 

 section to which Mr. Lowe gave the name of Leptaxis. And it 



