230 



PROCEEDINGS OF THE ACADEMY OF 



Jaw of F. pygmaum. [Morse.] 



Fis:. 70. 



full account of its history with all published information relating 

 to it has been given by Mr. Bland and myself in Ann. of Lye. Nat. 

 Hist, of N. Y., X., 306. The jaw is low, wide, slightly arcuate, 



with blunt, squarely truncated 

 Fig. 69. ends ; it is composed of six- 



teen separate pieces, each 

 higher than wide, with slightly 

 overlapping edges ; these 

 pieces do not run obliquel}'' 

 towards the middle of the jaw, 

 there is, therefore, no appearance of an upper median triangular 

 piece as in Orthalicus and Liguus. 



The lingual membrane is long and narrow. There are 54 rows 

 of 13 — 1 — 13 teeth each. The centrals have a base of attachment 



much longer than wide, expanded 

 below and squarely truncated, very 

 much narrowed above, reflected. 

 The reflection is very small and has, 

 according to Morse, one single cusp, 

 but Schacko (Malak. Blatt. 1872, 

 178) describes the reflection in some 

 European specimens as tricuspid. 

 Laterals of same form as centrals, 

 but with wider base of attachment in the first ones and bicuspid ; 

 outer laterals much narrower. There are no distinct marginals. 

 All the teeth are decidedly separated. 



I have not examined the jaw or lingual membrane of this spe- 

 cies, but am entirely dependent on Morse for the descriptions and 

 figures of the American form given above. While treating of the 

 identity of the American and European forms in the paper refer- 

 red to above, we have pointed out the differences in the jaw and 

 membrane of the two forms, which, however, do not appear to be 

 of specific value. 



£^#'" 



Lingual dentition of P. pygmceitm. 

 [Morse.] 



d. Jaw in a single piece, with an accessory, quadrate plate above. Mar- 

 ginal teeth quadrate. Succinin^. 



Genus SUCCINEA, Drap. 



Jaw with an upper, quadrangular, accessory plate. The jaw is 

 strongly arched, the ends acuminated in S. avara (fig. 71), blunt 



