2 CHONDRINA. 



The radular teeth of Chondrina differ a good deal from 

 those of other PupilUdfc, yet the peculiarity is probably not 

 indicative of great systematic separation. Similar simplifica- 

 tion of the teeth is seen in Allog-nathus, which in other char- 

 acters differs but little from the rest of the Pentataeniate Heli- 

 ces ; also in some tree snails. 



C. avenacea is probably as near as any recent species to the 

 ancestral forms of the genus, its aperture having the full 

 tooth-formula of the Abida group of genera. The other sec- 

 tions of the genus (Modicella and Solatopupa) appear to be 

 regional specializations from ancestors belonging to the aven- 

 acea group (Chondrina s. sir.). The specialization usually 

 was in the direction of tooth-reduction ; but in the case of 

 tiolatopnpa (C. similis and its allies) there has been adapta- 

 tion to direct, brilliant sunlight, the shell becoming conspic- 

 uously calcareous. 



Under Abida (Vol. XXIV, p. 263) the author has men- 

 tioned his diffidence in offering a compilation in place of the 

 monograph by an expert which these genera stand in need of. 

 It seems best not to leave the account of Pupillidge incom- 

 plete, and it is not practicable at present to have the work 

 done abroad. 



Radula. The dentition of this genus was first investigated 

 by G. Lindstrom (Om Gotlands nutida mollusker, 1868, p. 18), 

 who described and figured the teeth of Pupa avenacea. On 

 account of the narrow, simple cusps he formed a new genus, 

 Alloglossa, for this species. It is a pity that a prior name has 

 to be used, as Lindstrom was the first to define the group 

 scientifically. 



Schako (in Westerlund, Fauna Europaea, etc., 1878, p. 167) 

 stated that he had found dentition like that described by 

 Lindstrom for avenacea< in the species 



avenacea Brug. goniostoma B-m. 



quinquedentata Born. ventilatoris Parr. 



megacheilos Jan. muhlfeldii Kiist. 



Finally, the Rev. Prof. H. M. Gwatkin (Proc. Malac. Soc. 

 London, iii, 1897, p. 227) gave the results of his examination 



