NATURAL SCIENCES OF PHILADELPHIA. 



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in obliqua, ovalis, Totteniana (fig. 71), campestris, lineata, and 

 effusa ; there is a median projection to the cutting margin, some- 

 times broken by the ends of ribs. These ribs are found in S. Tot- 

 teniana (3) (see fig. 71) ; S. obliqua (3-7) ; ovalis (over 7) ; I de- 

 tected no ribs on that of S. avara, lineata, campestris, Nuttalliana, 

 Sillimani, or effusa. 



Fig. 71. 



Fig. 72. 



Jaw of Succinea Totteniana. 

 [Morse.] 



Jaw of Succinea avara. 



The general arrangement of the lingual membrane is shown in 

 fig. 73 of 8. avara, while the characters of the separate teeth 



Fie. 73. 



Lingual dentition of Succinea avara. 



are better seen in pi. XV., fig. 3. The peculiar character of the 

 dentition is the cutting away or thinning of the middle portion of 

 the lower edge of the base of attachment in the central teeth, 

 and the inner lower lateral angle of the base of attachment in the 

 laterals and still more in the marginals. The marginal teeth are 

 also often peculiar in the denticulation of their reflected cusps. 

 They have usually two small outer side cusps, the inner the smaller, 

 each bearing cutting points proportioned to their size. The reflec- 

 tion of the teeth is also small in proportion to the base of attach- 

 ment. In other respects the dentition of the genus is very much 

 like that of the Helicinse. 



Succinea Sillimani (pi. XVII., fig. 12) has 24124 teeth. 



Succinea ovalis has not been examined by me. Morse gives 

 80 rows of 40140 teeth. 



