OWATKIX : SO>rR N[OI.I.USCAX RADUL.-TJ. 



145 



A. 7C'alkeri Pgt. 

 A. engraphis Pils. 

 A. kirklandi \\'alker. 

 A. rivnlaris Say. 

 Ainph. alabamensis Pils. 

 Gundl. 7/ieekia/ia Stimp. 

 A^eopl. tantilliis Pils. 



Gundl, (Guatemala). 



A. kempi Preston. 



Hawaii. — 



A. sharpi Sykes. 



Nearctic. — 



A. caurimis Carp. 



A. fuse us Ads. 



A. ohioensis Walker. 



A. shiineki Pils. 



A. diaplianus Hald. 



A. heiinsphaericHS ^^'^alker. 



A. parallelus Say. 



Neotropical. — 



A. excentricus Morel. 

 A. sp. (Cordoba S.A.). 



TvPE (B). 

 East Africa. — 



A. crassistriatus Preston. 



Tasmania. — 



A. irvina Petterd. 



America. — 



A. klajnathensis Hann. 



sent Africa from Abyssinia to the Cape, India, Tasmania, Hawaii, and 

 America from Vancouver and New England to Argentina. From 

 these we may presume that it is also found in the East Indies, Aus- 

 traha, Polynesia, and Magellanica. Then its distribution is significant. 

 The Northern section bears to the Southern the relation of the higher 

 Helices {Belogona siphouadenia) to the lower. Mr. Taylor's map^ may 

 be copied almost unaltered, and he is likely to tell us that this is 

 another illustration of Dominancy in Nature \ and such, indeed, it 

 seems to be. True, I know no evidence of the former existence of 

 this group in Europe, and certainly none of its present survival ; but 

 the conclusion suggested by its present distribution is confirmed by 

 the primitive character of the radula. The general pattern of the 

 teeth is like the laterals of A. lacustris, but the rows are nearly straight 

 instead of arched. The central tooth is bicuspid, as in Planorbis, the 

 laterals have oblique tops and are more denticulate than those of 

 A. lacustris, resembling those of the smaller species of Planorbis, 

 while the marginals are not plate-like, but comb-like or feathery — 

 again like Planorbis. The jaw, also, is in plates, as in the first sec- 

 tion. This description generally covers the section ; but it passes 

 into an extreme form which we may call Tvpe (B), of which I have 



J " Doniiiianc}- in Nature" (fig. 6), Trans. Vorks, Naturalists' Uni' 



