4 Observations on the Terrestrial 



(2.) In another group wliicli we designate as Helicellinae, we 

 have the viscera protected by a thin, glabrous shell ; the lingual 

 membrane is nearly as broad as long, having about sixty-eight 

 rows of plates, averaging about forty-two plates in a row; the 

 laterals and uncini are quite distinct ; the central plate broad, 

 long, trideutate ; the laterals, three to five, bidentate, identical 

 with central, in form of denticles ; the uncini unidentate, the 

 denticle being aculeate and re-curved. The buccal plate is thin 

 and crescent shaped, with a middle beak-like projection, lateral 

 terminations pointed. 



(3.) In a still smaller group, for which we j^ropose the sub- 

 family name of Valloninae, we have the lingual membrane composed 

 of eighty or ninety rows of plates, averaging twenty-six plates in 

 a row. The laterals and uncini are generally distinct. The 

 central plate is square, tridentate ; the laterals four to five, square, 

 bidentate ; uncini broad, short, and minutely serrated. The buccal 

 plate is slightly arcuate, rarely produced centrally; its front surface 

 marked with delicate perpendicular or diverging strias, faintly 

 notching the cutting edge ; the lateral terminations of plate being 

 rounded or blunt. 



These three types of lingual dentition are accompanied witli 

 like peculiarities in the character of the shell, the external appear- 

 .ance of the animal, and the general size of the species. 



Vitrininae I restrict to Vitrina, owing to the value I place on 

 the external characters of the animal. Punctinje I hold good on 

 the extraordinary character of the lingual dentition and buccal 

 plate peculiar to the species on which this sub-family is based. 

 The other groups we have not considered sufficiently to offer any 

 opinions as to their relative value or position. Taking the number 

 of plates in a row from five different species in each group from 

 Pupinre upward, and averaging this number for each group, we 

 liave the following result : 



Limacidas including Philomycenidje, 94 

 Helicinffi, 73 



Helicellinae, 42 



Valloninae, 26 



Pupinas, 24 



