NATURAL SCIENCES OF PHILADELPHIA. 195 



lateral expansion of the base of attachment. Marginals (b) low, 

 wide, with one inner, stout, oblique cutting point and two outer, 

 smaller, blunt cutting points. 



As in all lingual membranes, there is a difference in the develop- 

 ment of the cusps and cutting points on various parts. The teeth 

 figured are the least graceful in their outlines. 



Genus BINNEIA, J. G. Coop. 



Jaw (fig. 40) low, arcuate, with blunt, scarcely attenuated 

 ends; no median projections to the cutting edge; anterior surface 

 with numerous, broad, crowded ribs. 

 Jjt-rr-^ Lingual membrane (fig. 41) as usual in the Heli- 



cinse. Centrals with a subquadrate base of attach- 

 ment, with expanded lower angles ; upper margin re- 

 notauus. fleeted ; reflection large, bearing three distinct cusps, 

 the central the longest; all three cusps apparently with 

 distinct cutting points. Laterals like the centrals but unsymme- 

 trical by the suppression of the inner cusp and cutting point, and 



Fig. 41. 



Lingual membrane of Binneia nntahilis. 



inner lower lateral expansion of the base of attachment. Margi- 

 nals simply a modification of the centrals, subquadrate, higher 

 than wide, with one inner, long, oblique, stout cutting point, and 

 one outer, smaller, side cutting point. 



I regret not being able to give a more satisfactory figure of the 

 dentition of B. nolabilis, our only known species. 



It has 21 1 21 teeth, with 8 perfect laterals. 



Genus HEMPHILLIA, Bl. and Binn. 



Jaw of the only known species, H. glandulosa, thick, low, wide, 

 slightly arcuate, ends attenuated, blunt; cutting margin without 

 median projection ; anterior surface with about 14 crowded, stout, 

 irregularly developed ribs, denticulating either margin (pi. XVI., 

 fig. 6). 



