118 Dentition of Pulmonale Mollusks\, 



to be now found subfossil only.* I can only treat the question of the 

 identity of the St. Kitts and Dominica forms, not their identity with Guade- 

 loupe forms. 



It will be seen that the Dominica form has sharper cutting points to the 

 large cusps of its central and lateral teeth than that of St. Kitts. Fig. B 

 shows a group of laterals of the former, in which some variation from the 

 pointed shape is indeed shown, but no decided tendency that way. On the 

 other hand, the laterals, from the St. Kitts form, show great constancy in 

 the square truncation of the cutting points. (Fig. B.) 



The teeth of the St. Kitts form are broader in proportion to their length 

 than those of Dominica, have a greater curve in their outlines, and more 

 developed side cusps, which overlap the median cusps. 



The Dominica lingual in the only row counted had 87-1-87 teeth. A row 

 of the St. Kitts form had 57-1-57. The marginal teeth of the St. Kitts form 

 show a greater tendency to splitting into sharp denticles on the cutting 

 cusps than those of Dominica. 



It cannot be denied that certain variations may be noticed in the two lin- 

 gual membranes. I believe, however, that these differences are not such 

 as suggest specific distinction, especially as the shell furnishes no grounds 

 for doubting the specific identity of the forms. 



Mr. Bland has given a detailed account of the species in Journal de 

 Conchyliologie, XXI, 342, October, 1873. 



Ampliibulima Raivsonis, Bl. Isle of Montserrat, between 

 Nevis and Guadeloupe. Gov. Rawson. 



Jaw as in A. rubescens, about 33 ribs ; those at the upper centre running 

 obliquely and meeting or ending before reaching the lower margin. 



Lingual membrane (PL XIII, figs. H, G) as usual in the genus. Centrals 

 with the base of attachment very much larger than that of the laterals, and 

 with an enormous, single, broad, long, rapidly and obtusely pointed cutting 

 point. No side cusps or side cutting points. Laterals of the form usual 

 in the Eelicince, with a stout, inner cusp, bearing a broadly truncated, short 

 cutting point, aud a small side cusp bearing a short cutting point. 



The change from laterals to marginals is shown in the 10th, loth and 

 27th teeth in the plate. 



The marginals i28th and 68th teeth in the plate) have a long, narrow base 

 of attachment, which near its lower margin bears a short, slightly expand- 

 ing, bluntly trifid cusp ; from this cusp springs a short, expanding, bluntly 

 denticulated, broad, cutting edge, the inner denticle the largest. This cut- 

 ting edge is shown in the 67th and 68th teeth on a more enlarged scale, 

 There is great variation in the denticulation of the cutting edge. There 

 are 68-1-68 teeth. 



* See, also, under A. Rawsonis, for Fischer's description of the dentition 

 of the Guadeloupe form. 



