292 JVotes on Lingual Dentition of Mollusca. 



Teeth 19.1.19. Centrals sub-oval, rounded at base, narrowing 

 toward the top, which is squarely truncated ; apex broadly re- 

 curved into an obtuse beak, beyond which are two long, narrow, 

 tusk-like projections. First seven laterals uniform, in an almost 

 straight transverse series, detached, inclining obliquely toward 

 the median line, large, square, broadly reflexed, extending 

 bej^ond the base in a wide, blunt beak, at each side of which are 



V\a. in. 



Liiiguiil tk'iitiiion oi Planorbis trivolvis, Say. 



usually one or more small denticles. These laterals pass gradually 

 into the uncini, which are in curving rows, long, narrow, widely 

 recurved, with variable, strong, beak-like digitations on their 

 apices and outer sides. 



There is great variation in the digitations on the uncini, no two 

 of which appear alike. The laterals also vary somewhat in the 

 breadth of their recurved beaks. 



Fig. 10, a, represents two central teeth with two of the first 

 laterals on the left of the median line ; h the merging of the laterals 

 into the uncini ; and c extreme uncini. h and c are taken from 

 the right of the median line. 



Tiilofoina inagTiillca, Conrad. 



Through the kindness of Dr. E. E. Schowalter, of Uniontown, 

 Alabama, we are able to describe the lingual dentition of Tulo- 

 toma magm'fica^ Conrad. The specimens received from Dr. 

 Schowalter were taken in the Coosa river, Alabama. 



It will be seen that in its lingual dentition Tvlotoma is more 

 closely allied to Yivipara (as suggested by Gill, Proc. Acad. N. 



