Notes on Radulcs. 



83 



about midway of the reflexion, the other then placed at the 

 distal end; there are generally several small denticles on the 

 upper inner edge of the reflexion ; the outer marginal have 

 all the cusps placed at the distal end, and the margins are 

 simple. The marginals vary greatly in the form and position 

 of the cusps. All have decided cutting points. A number 

 of specimens examined. 



I^imnophysa desidiosa Say. Plate IV, C. 



Radula formula f£-+S+i+i+H-|+ff (46-1-46) ; teeth 

 similar to those of L. columella ; the marginal teeth are very 

 variable; 1 to 7 are perfect laterals, bicuspid, 8 to 16 are 

 transition teeth, tricuspid, with a large central cusp and two 

 small side cusps, one on each side ; the marginals are at first 

 modified transition teeth (17 to 20, but soon the tooth becomes 

 long and narrow and the distal end becomes 3-4 cuspid and 

 has several small denticles on the outer central margin of the 

 reflexion (21-34) ; the outer marginals (35-46) are denticulated 

 only at the distal ends. A number of specimens have been 

 examined. 



Limnophysa humius Say. 



Radula formula If+f-r-f+Hf+if (22-1-22) ; teeth 

 in all respects similar to those described above. 



Limnophvsa caperata Say. Plate IV, B. 



Radula formula f^n L f +^-1+1+1 +|r~ (32- 1 - 32) ; teeth 

 as usual; the 8-10 teeth are transitory and the 1 1 to 32 are 

 all of the usual form of marginals; several teeth had the 

 distal end broken up into two large cusps and several small 

 cusps (14). A number of specimens were examined. 



IyiMN^EA cubensis Pfeiffer. 



Radula formula £f- +£+|+f+i+t -j-i-ff+j^ (30- 1 -30) ; 

 teeth as usual; the first four laterals are bifid, the next is 

 trifid ; 5 to 7 are transitory and 8-30 are of the usual form of 



3 



