Lingual Dentition in Physa, 255 



however, the same teeth retain their subquadrate form, 

 figure 7. Both jaw and lingual membrane, therefore, 

 prove that the genus belongs to the Helicince of our pro- 

 posed arrangement of Pulmonata (see Ann. Lye. N. H. of 

 N. Y., I. c. 165), or to the Helicea of von Martens. (Die 

 Heliceen, ed. 2.) 



By its jaw, Gceotis calls to our mind the genus AmpJiibu- 

 lima (see pi. xi, fig. 8), as well as the shell known as 8uc- 

 cinea? appendiculaia' Pfr., whose generic position we have 

 left in doubt (Ibid, X, pi. ix, fig. 2), and many species of 

 Bulimulus. We have above shown the resemblance of its 

 lingual dentition to that of Ortlialicus and Liguus, as well as 

 of Helix muscarum. It also forcibly reminds one of some 

 of the features of the dentition of Triboniophorus, 



Our figure 5, plate xi, gives the central and adjacent lat- 

 eral teeth : fig. 6 an extreme marginal in profile, on a dif- 

 ferent scale of enlargement : fig. 7 a marginal seen as in 

 fig. 6 : fig. 1 the largest fragment saved of the jaw. 



XXII. — N'ote on a carious form of Lingual Dentition in 



Physa. 



Bt THOS. BLxVND axd w. g. binney. 



Eead January 6, 1873. 



We have received from Governor Rawson specimens in 

 alcohol of a shell apparently belonging to the genus Pln/f^a , 

 collected at Point a Pitre by M. Schramm. On exRmining 

 its jaw and lingual dentition, we find both difl^erent from 

 what is usual in that genus. The jaw is not at all chevron- 

 shaped,* but is simply slightly arcuate, long, low, ends atten- 

 uated. The lingual membrane wants entirely the broad 

 transverse rows of comb-like teeth arranged en chevron 



* See figure of jaw of Fhysa in X/and and Fresh Water Shells of North Amer ica, II 

 p. 75, fig. 123. 



January, 1873. 18 Ann. Ltc. Nat. Hist., Vol. x. 



