90 Dentition of Pulmonale Mollushs. 



Poly mi ta muscarum, Lea. 



Jaw wide, low, arched, delicately striated ; ends attenuated, bluntly 

 rounded ; no anterior ribs; no median projection to the cutting edge. (PI. 

 XV, fig. K.) 



Lingual membrane long and narrow, composed of numerous rows of 

 about 75-1-75 teeth each. The transverse rows are arranged en chevron. 

 Centrals with base of attachment long, narrow, incurving at the sides ; 

 upper margin slightly rounded ; lower margin trilobed and fringed; on the 

 lower fourth of the base of attachment springs a trilobed, gouge-shaped, 

 cutting edge, broader than the base, and bearing three cusps, each produced 

 into a cutting point, the central triangular, the external ones curving out- 

 wards, neither produced bej^ond the lower margin of the base of attach- 

 ment. The side teeth (which do not resemble the usual form either of later- 

 als or marginals) are of the same form as the centrals, but rendered asym- 

 metrical by the lesser development of the inner lower angle of the base of 

 attachment, and by its being thrown abruptly off towards the margin of the 

 membrane; the lower edge is also rounded, and not trilobed as in the cen- 

 trals; the laterals, also, are longer, narrower, with a less expanded upper 

 margin of the base of attachment than in the centrals, in a contrary direc- 

 tion from which they are also thrown off by the irregular curving of the 

 base of attachment. The cusps and cutting points of the side teeth are like 

 those of the centrals. 



In one lingual membrane examined, I noticed two abnormal rows of 

 teeth down the whole length of the membrane, in which the cutting edge 

 was divided into four lobes, instead of three, all bearing cutting points. 

 These abnormal lines of teeth were separated by a normal line. 



The figure (PI. Ill, fig. C) shows a group of central and side teeth, while 

 a single central, still more enlarged, is shown in D. 



These peculiar, long, subquadrangular bases of attachment, not reflected 

 along the upper margin, as usual in the Heliciclce, but bearing the gouge- 

 shaped, expanded cutting edge, soldered as it were upon its surface, can 

 only be compared to those of Gceotis, and those of the marginal teeth of 

 Orihalicus and Liguus. 



Polymita picta, Born. Cuba. The specimen examined was 

 fuund on a bunch. of bananas in New York. 



Jaw as in muscarum. 



Lingual membrane (PI. Ill, fig. E) with the same characteristics as that 

 of muscarum; but the teeth are shorter and stouter. (Plate III, fig. E.) 



HEMITROCHUS. 



I have examined only five species of those remaining in von 

 Martens' Polymita, after removing its type, muscarum, as ex- 

 plained above. Helix versicolor, Born, is the only remaining 



