Dentition of Puhnonate Mollusks. 8!) 



Pa tula. 



Patula Huahinensis, Pfr. Huahine Island. Mr.. A. Garrett. 



Jaw not examined. 



Lingual membrane with 18-1-18 teeth, of which about six on each side 

 are laterals. The t} 7 pe of dentition is about the same as in Endodonta incerla, 

 described above. The marginals are, however, different, the two cutting- 

 points being bifid, the base of attachment low and wide. (Plate II, fig. L.) 



Pella. 



The character of the jaw does not allow the genus to hold a 

 position here, among "ribless jaws." 



Pella rariplicata, Benson. Cape Town, S. Africa. Mr. J. S. 

 Gibbons. 



The jaw has flat, crowded, numerous ribs, such as I have described for 

 Microphysa Lansingi, in Terr. Moll. , V. 



Lingual membrane (PI. Ill, fig. I) long and narrow. About 16-1-16 teeth, 

 with four laterals on each side of the central tooth. The central tooth has 

 small side cusps and cutting points. Laterals like the centrals, but slightly 

 asymmetrical by the lesser development of the inner side ; an unusual arrange- 

 ment in the Helicidce. The marginals are low, wide, with one inner, wide, 

 bifid cutting point, and one smaller, bifid outer cutting point, giving a 

 serrated appearance to the cutting edge. 



A central tooth, with its adjacent laterals, and two marginal teeth, are 

 given in the figure. 



Polymita. 



Having found two different forms of dentition in the species 

 referred by Von Martens to Polymita, I propose to restrict this 

 genus to those species which have the abnormal dentition of its 

 type, P. muscarum, leaving those with the usual dentition of 

 the Helicidce under the name of Hemitroclius. 



The peculiar dentition of Polymita, entirely unexpected from 

 the appearance of the shell, is one of the most interesting facts 

 I have met with. It is not only different from that of its allied 

 forms, but also from that of all species of the Pfeifferian genus 

 Helix as yet examined. 



The peculiar dentition is shared by p iota, Born, and maybe 

 looked for in sulphurosa, Morelet. These two species are placed 

 by von Martens, in Liochila, together with Helix Jamaicensis. 

 The two former I put with muscarum in Polymita. For the 

 last, see below. 



