WATSON : AFFINITIES OF PYRAMIDULA, ETC. 



25 



In some respects these snails from the Hawaiian Islands show a 

 specially strong resemblance to the Valloniinse. Thus the lateral and 

 marginal teeth of the radula of some of the species are remarkably 

 similar to those of Patulastra halinei, more like them than those of 

 any European form that I have seen. And although the central 

 teeth in Amastra itself are even smaller than in the European genera, 

 this does not seem to be the case in Leptachatina. Again, while the 

 shells of some of the Amastrinse scarcely differ from Cochlicopa, 

 we find every gradation from this form to shells that are even 

 flatter and more openly umbilicate than Patulastra or Vallonia ; 

 and the apical spiral striae of Armsia and Thaanumia (a sub-genus 

 of Leptachatina) resemble those of Vallonia costata and Acanthinula 

 aculeata. 



Diagram showing the diverse distribution of diiierent characters among 

 "reiDresentative genera allied to the Pupillidse, and illustrating the 

 fact that a division of the group based on any single character would 

 not accord with one based on any other. The dotted lines indicate one 

 of the many possible views that might be held concerning the genetic 

 connexions of the various genera. 



We find, therefore, that although the sub-family Valloniinse is 

 undoubtedly closely related to the typical members of the Pupillidse 

 it is in many ways intermediate between the Pupillidse, the Enidae, 

 the Cochlicopidae, and the Amastridse, agreeing closely with one 

 group in one respect and with another in another respect, though 

 resembling them all in most respects. It thus seems to help to link 

 together these so-called families ; to emphasize the fact that their 

 supposed differences, when they exist at all, are scarcely to be 

 compared with the differences that separate the families of the 

 Sigmurethra, and to support the view that all these groups might 

 well be united into a single family, divided into an unusually large 



