﻿MONOGRAPH OF THE ATLANTIDAE. 



11 



It is especially in Atlanta that the disproportion of the 

 whorls is most clearly prououuced. We may distinguish 

 safely between the spire (all the whorls but the last one) 

 and the last whorl, which is always rolled up, in its 

 whole extent, in the same plain, whereas the spire is more 

 or less elevated, but nearly always very small, and consisting 

 of generally 4 — 5 whorls, which follow each other regularly 

 and gradually increasing. 



By far the most species of the Atlantidae belong to this 

 genus. Formerly, in my monograph (p. G), I published 

 a list containing 27 names; one of them, however, being 

 identical with » Atlanta souleyeti" Smith, while three other 

 terms (see above) are likely to be referred to Oxijgyrus^ 

 the number should be reduced to 23, which, with addition 

 of two species added by me (pp. 53, 55, PL VII, figs. 9 

 and 10, PI. VIII, figs. 14 — 18), makes a total number of 

 25 names I shall not repeat this list here, but shall 

 only try to discriminate certain groups. 



Firstly we may separate a few species, which are most 

 insufficiently described, sometimes even never figured, 

 and which, in my opinion, should be rejected entirely. 

 They are : 



A. lamanoni (Eschsclioltz). 

 „ lielkialis Sowerby. 



„ sp. 1 Gray (most likely Oxi/gyriis keraudreni Lesueur). 

 „ sp. 2 Gray (most likely — A. iieroni Lesueur). 

 „ planorboidesYoihes. 



Secondly three names are synomyms of other forms, 

 already known : 



A. rosea Souleyet — A. peroni Lesueur. 

 „ incUnata Yayssiere (his fig. 91) = A. fusca Souleyet. 

 „ oligogjjra Tesch - A. lesiieuri Souleyet. 



Further I regard a few species as uncertain ; in some 

 cases the type-specimens have been lost, and I have not 



1) strictly spoken there are 26 names, as Vayssiere under the title „A. 

 incUnata' comprises two certainly distinct species. 



Notes from the Leyden Museum, Vol. XXX. 



