AMPHIBUL1MA. 



broad, rounded mesocones, and well developed ectocones. The 

 laterals are similar, but asymmetrical by suppression of the entocone, 

 as usual (pi. 60, fig. 11). The ectocone gradually increases, until 

 on the transition teeth (left side of fig. 11) it is not greatly smaller 

 than the mesocone. The inner marginals (last tooth to the left in 

 fig. 11) have two subequal cusps. The outer marginal teeth (fig. 12) 

 have three or four slender denticles, on a long, curved basal-plate, 

 which on the outermost teeth is indistinguishable from the basement 

 membrane except near the cusps. 



Binney found substantially the same type of teeth in St. Kitts 

 examples. Those from Dominica have a longer, pointed cusp on the 

 central tooth, while Fischer found the cusps long and conic in the 

 Guadalupe form, which with the same number of teeth in a trans- 

 verse row has 20 laterals. The central teeth have no ectocones, 

 according to Fischer. These divergencies indicate racial differenti- 

 ation on the several islands, thus : 



a. Cusps of central and adjacent teeth pointed. A. patula and 

 var. dominicensis. 



b. Cusps of central and adjacent teeth broadly rounded or trun- 

 cate ; St. Kitts. Var. christopheri Pils.; pi. 60, f. 11, 12; pi. 62, 

 f. 27-30. 



A. patula is from Guadalupe and Marie-Galante, with varieties in 

 Dominica, St. Kitts and Saba ; A. tigrina is said to be from St. Vin- 

 cent ; A. pardalina and A. browni from Dominica, and A. rawsonis 

 from Montserrat. 



A. patula Brug., xii, 234. A. tigrina Les. xii, 237. 



cucullata Lam. A. pardalina Gupp., xii, 237. 



v. dominicensis Pils., xii, 237. A. browni Pils., xii, 238. 



v. christopheri Pils., above. A. rawsonis Bid., xii, 239. 



Subgenus RHODONYX Fischer, 1873. 



Shell immaculate, rose-tinted, Succinea-shaped. Jaw (pi. 62, fig. 

 32) similar to that of Amphibulima, having 60-63 plaits. Radula (pi. 

 61, fig. 25, after Binney) with 47.13.1. 13. 47 teeth. The central tooth 

 is tricuspid, middle cusp very large and broad, emarginate or truncate 

 at the apex, side cusps pointed. The latter and inner marginal teeth 

 are similar but without the entocone. The outer marginal teeth have 

 long, narrow basal plates, like those of Amphibulima, and tridentate 



