92 Dentition of Pulmonale Mollusks. 



median rib-like prominence, denticulating either margin. (PI. XVI, tig. J.) 

 See above, under generic name. 



Lingual membrane with 33-1-33 teeth, characterized as in the other spe- 

 cies. Fig. D, of pi. IV, shows one central and adjacent lateral, an outer 

 lateral (7th tooth) showing the side cusp and cutting point ; the eighth later- 

 al, in which the inner cutting point first is bifid, the sixteenth tooth, still a 

 lateral, though somewhat modified in form, and a marginal, the last tooth. 

 It will be noticed that, on the central and first lateral, the cutting point has 

 a side bulging, probably a modification of the missing side cutting point. 

 No doubt this bulging exists in the other species of the genus, though not 

 shown in the focus under which my figures were drawn. 



Acavus. 



Acavus Phwniz, Pfr. 



Jaw wide, low, arcuate ; ends but slightly attenuated, blunt, very thick 

 and coarse; no anterior ribs; no median prominence to the cutting edge. 



Lingual membrane (PL II, fig. O) with long and narrow centrals and lat- 

 erals ; the upper margin of the base of attachment produced and rounded ; 

 the reflection is stout, as are the cusp and cutting point, of which only the 

 middle one exists. Marginal teeth simply a modification of the laterals. 



Caracolus. 



In this genus, also, there is a difference as regards the presence 

 or absence of ribs on the jaw. 



Lingual membrane characterized by the absence of side cusps 

 and cutting points. 



Caracolus Bermudensis, of von Martens' list, I have above 

 shown to be more nearly allied to Zonites than to any known 

 genus. Caracolus inversi color I have above referred to Nanina. 



Caracolus excellens, Pfr. San Domingo. Dr. Newcomb. 

 Jaw not examined. 

 Lingual membrane (PI. IV, fig. F). 



Caracolus sagemo?i. Beck* Cuba. Mr. Arango. 



Jaw high, arcuate; ends rapidly but slightly attenuated, blunt; cutting 

 margin with broad, blunt, median projection; no anterior ribs. 



Lingual membrane (PI. IV, fig. G> very long and narrow, with 36-1-36 

 teeth ; the transverse rows of teeth being unusually oblique, though not so 

 represented in my figure. The change from laterals to marginals is very 

 gradual, so that it is difficult to count the former. Centrals with base of 

 attachment long, constricted at the middle, expanded above, and with 

 greatly produced lower lateral angles; reflection large, with obsolete side 



