88 



Cincinnati Society of Natural History. 



figures, however, do not show the peculiar alternate arrange- 

 ment of the denticles on the primary teeth, nor the number 

 of the same. 



Physa ancillaria Say. 



The radula of this species is precisely like that of hetei o- 

 stropha. 



Aplkxa hypnorum Linne. Plate V, D. 



Radula with a central tooth, as in Physa (?), excepting that 

 the denticles are differently arranged, the central denticle 

 being rather long, and having four shorter ones on either 

 side; the base of attachment could not be made out; lateral 

 teeth serrated similar to those of Physa, but the teeth equal 

 in size and 9-10 in number, and rather long and pointed; the 

 base of attachment is very long and rounded at the extremity. 

 The writer counted 78 teeth (39-1-39) in a single row, and 230 

 rows in one membrane. The upper part of the base of attach- 

 ment supports a peculiar lateral appendage in the form of a 

 long and narrow projection, which may represent the sec- 

 ondary tooth in Physa. The dentition differs from Physa, 

 principally in the form of the denticles on the primary teeth 

 and in the absence (?) of the secondary teeth. The peculiar 

 lateral appendage may be, as before remarked, a secondary 

 tooth. 



Pleurocera subulare Lea. 



Jaw elongately ovate, the surface covered with numerous 

 small, rounded, or polygonal scales. 



Radula formula T V+ \ + 1 + 1 + 1 -f i "h tV (3-1-3); 

 central tooth with a low, wide base of attachment, the reflected 

 portion 7-deutate, the central cusp very long, the side cusps 

 very much shorter ; intermediate tooth almost square, 5-den- 

 tate, the inner cusp small, the next cusp very large, and the 

 three other side cusps small ; lateral teeth more or less sole- 

 shaped, longer than wide, the first 8 and the second 10 den- 

 tate ; the outermost lateral flares a little at the upper part. 

 In one membrane the writer counted 43 rows of teeth. The 

 radula is very similar to that of P. elevatum. 



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