NATURAL SCIENCES OP PHILADELPHIA. 225 



incurved, its upper margin broadly reflected. The reflection is 

 large and has subobsolete side cusps bearing well developed 

 cutting points, and a short, stout median cusp, bearing a short, 

 stout cutting point not quite reaching the lower margin of the base 

 of attachment. The laterals are of the same general form as the 



Fi?. 07. 



Liugual deuliuou of Bulimulus dtalbatus. 



centrals, but are larger, broader in proportion, and are rendered 

 unsymmetrical by the suppression of the lower inner angle of the 

 base of attachment, and inner side cusp and cutting point. The 

 marginal teeth (fig. h) are but a simple modification of the laterals, 

 formed by the proportionally greater development of the reflection 

 in comparison with that of the base of attachment, and the greater 

 development of the cutting points. On the extreme marginals 

 the cutting points are shorter and much blunter (fig. c). 



The dentition of Bulimulus alternatus is figured on p. 203 of 

 L. and Frw. Shells, I. I have preserved no specimen from whicl> 

 I can more accurately draw the individual teeth. It has 15 rows 

 of 3T — 1 — 37 teeth, all apparently of the same character as in B. 

 dealhatus. 



I have not examined B. nudtilineatus, Dormani, llarielimis, 

 Floridanus, patria7-cha, Schiedeanus. 



c. Jaw in numerous distinct pieces, sometimes soldered together above, 

 free and imbricated below. Marginal teeth quadrate. Orthalicin^. 



Genus LIGUUS, Montf. 



Jaw thick, arcuate, ends rapidly attenuated, pointed ; composite, 



being in numerous, separate, free, imbricated, triangular pieces, 



with sutures inclined obliquely to the centre of the jaw, so as to 



leave an upper median, angular piece ; other 



Y\(r 68 pieces are soldei'ed together above. Cutting 



edge with no median projection, serrated by 



the lower angles of the oblique pieces. For 



1^ -^ more detailed description see below, under 



Jaw of L. virgineus. OvUialicus, wliich has a similar jaw. I am 



