Notes on Lingual Dentition of Mollusca. 283 



square, lateral expansions. Laterals much like centrals in shape, 

 unsjmmetrical, the inner side cusp being still more obsolete; 

 base and inner side of plate forming one regular outward curve; 

 upper edge of plate horizontal, with one lateral expansi6n only 

 at its outer corner. Uncini on long, narrow, low, subquadrate 

 plates, with one long, curving, blunt denticle, and one short 

 blunt denticle at its outer side. 



Fig. 2, a shows two incomplete rows of centrals and laterals ; 

 h one of the uncini, near the extreme lateral edge of the mem- 

 brane. 



The jaw has already been described (Land and Fresh-water 

 Shells of North America, Part L, p. 196). 



This species is from Lower California. 



Helix tiimida, Pfeiffer. 



The specimen which furnished the lingual membrane here 

 described was received from Messrs. Grioyne and Yendryes, of 

 Kingston, Jamaica, to which Island the species belongs, 



H. tumida is placed by v. Martens (Die Heliceen, 2d ed., 145) 

 with several other Jamaica species, and H. pempldgodes^ Pfr., of 

 Cuba, in the subgenus Cysticopsis of Morch. 



Fig. 3. 



Lingual dentition of Helix tumida, Pfr. 



Lingual membrane with numerous straight rows of 22.1.22 

 teeth. Centrals with three stout cusps, the middle one yqtj 

 large, on a subquadrate plate which has square lateral expan- 

 sions above. Laterals of same form as centrals, but lacking the 

 inner side cusp and inner lateral expansion. Uncini with one 

 large and several smaller blunt cusps, attached to a long, sub- 

 quadrate plate. 



The figure presents one-half of one central, the first lateral, and 



