108 Dentition of Pulmonate Molliisks. - 



Pomatia Humboldtiana, Val. Mexico. Dr. E. Palmer. 



Jaw short, arched, bluntly ending; with six broad, separated!, stout ribs, 

 denticulating either margin. 



Lingual membrane (PI. VIII, fig. A) with shorter, stouter teeth than in 

 the last species. The centrals are pear-shaped, with no side cusps or cut- 

 ting points. 



Thelidomus. 



Jaw with stout anterior ribs. 



Lingual membrane the same in the species examined, in gen- 

 eral characteristics, but there will be found variation as to the 

 presence of side cutting points on centrals and laterals. 



Thelidomus aspera, Fer. Jamaica. Mr. V. P. Parkhurst. 



Jaw wide, low, arcuate, ends but slightly attenuated, blunt; anterior sur- 

 face with eight sharp, prominent ribs, strongly denticulating either margin. 



Lingual dentition (PL VIII, fig. E) long and narrow. Teeth 41-1-41. 

 Centrals and laterals with stout broad cusps and cutting points; no side 

 cusps or cutting points ; marginals with one long, bluntly bifid cutting 

 point. 



Thelidomus discolor, Per. 



Jaw arcuate, thick, ends blunt. Anterior surface with seven unequal, 

 decided, stout ribs, denticulating either margin. 



Lingual membrane (PL VIII, fig. D) long and narrow. Centrals with a 

 long narrow base of attachment expanded at the base, and bearing at its 

 corners a small reinforcement ; lower margin extending beyond the cusp ; 

 reflection bluntly tricuspid, the median cusp long, stout, with a short blunt 

 point; side cusps subobsolete. Laterals as the centrals, but asymmetrical, 

 and with a shorter base of attachment. Marginals quadrate, wide as high, 

 with two short, blunt denticles, the inner one slightly the longer. 



Thelidomus auricoma, Fer. Lomas de Camoa, Cuba. Mr. 

 Arango. 



Jaw arched, with blunt, scarcely attenuated ends; twelve broad ribs dis- 

 tributed over the whole anterior surface and denticulating either margin. 



Lingual membrane (PL VIII, fig. F) with 42-1-42 teeth, of which 25 may 

 be called laterals, but the change is gradual into marginals. Teeth as in 

 provisorkt. 



Thelidomus notabilis, Shuttl. Tortola. Mr. Robert Swift. 



Jaw arcuate, low, ends blunt, narrower at the centre; decided separate 

 ribs denticulating either margin. 



Lingual membrane (PL VIII, fig. G). Centrals tricuspid; laterals bicuspid; 

 the base of attachment about as wide as high, the larger cusp with a long 

 cutting point extending beyond the lower margin of the base of attachment. 



