256 Lingual Dentition in PJiysa. 



which are characteristic of Physa.* On the other hand, the 

 lingual membrane is long and narrow, with almost horizontal 

 rows of teeth. The centrals are narrow, somewhat expanded 

 at the base, at apex recurved into a slightly produced quin- 

 quedentate cusp, the central denticle the largest. The later- 

 als are quadrate, the whole apex recurved into a broad cusp 

 produced almost to the base of the tooth, with one large, 

 inner, stout, pointed denticle which bears on its inner side 

 another small pointed denticle, and two, small, irregular, 

 sharp, side denticles. The marginals are but modifications 

 of the laterals, wider than high, with one bluntly bifid inner, 

 and several small, blunt, irregular side denticles. 



The centrals and laterals are like those of Limnoza] rather 

 than of Physa, the marginals more like those of PlanorbisX 

 but much more quadrate. 



In our figure 2 of plate xi, w^e give one central and several 

 lateral teeth, in fig. 3 one marginal : fig. 4 represents the 

 jaw. 



A view of the shell is also given in fig. 9. 



We have not been able to determine this species of PJiysa, 

 represented by M. Schramm to be very rare. In some re- 

 spects it appears to be allied to P. striata D'Orb. (Cuba I. 

 192, Tab. xiii, figs. 14-16), received by that author from 

 M. Ferdinand de Cande, but whether from Martinique or 

 Cuba was not positively known. 



EXPLANATION OF PLATE XI. 



Fig. 1. A portion of jaw of Gceotis (p. 253.) 



2. Physa ? (See p. 255.) One central tooth and two laterals 



from the lingual membrane. 



3. The same as 2. One marginal tooth. 



4. The same. The jaw. 



* See Ibid, p. 81, fig. 138 : p. 82, flg. 141. Physa ampnllacea, Gld. from Colorado Ter- 

 ritory, lately collected by Dr. E. Palmer, has the same type of lingual. Dall lias detected 

 a more simple form of tooth alternating with the comb-like laterals of Physa. See his 

 exliaustive review of LimnceidcB etc., in Ann. of Lye. N. H. of N. Y., IX 333 foi valu- 

 able information on the dentition of the tresh water Pulmonates. 



fSee our figures in the Amer. Jour, of Conch., 1871, pi. xii. 



JSee our figure in Ann. of Lye, N. H. of N. Y., IX, p. 292. 



