118 The MoUuscan Family Planorhidae 



The radula teeth of Drepanotrema are peculiar in the possession of the 

 small interstitial cusps between the larger cusps. They somewhat resemble 

 the multicuspid teeth of Segmentina, Hippeutis, Intha, etc., to which the 

 genus is also allied by the presence of a fiagellum. The radula of Drepano- 

 trema is very uniform in the shape of the teeth, varying principally in 

 the number of interstitial and accessory small cusps. The formulae, as well 

 as the number of lateral and marginal teeth, vary in the different species. 



For the above anatomical data, three species have been examined: 



Drepanotrema anatinum (Orb.) Pueblo Viejo, Puerto Rico, collected by Dr. W. A. 



Hoffman. Five specimens dissected. 

 Drepanotrema hoffmani F. C. Baker. Isabela, Puerto Rico, collected by Dr. W. A. 



Hoffman. Eight specimens dissected. 

 Drepanotrema lucidmn (Pfeiffer). Havana, Cuba. Received from Dr. C. G. Aguayo. 



Five specimens dissected. 



Geographical Distribution. This genus is found more or less abun- 

 dantly from southern Texas southward through Mexico and Central 

 America to Brazil, Bolivia, and the Argentine Republic. It it also found 

 in many of the West Indies Islands. It is jnirely an American genus and 

 a number of species are known, including some names now considered 

 synonyms. 



Pilsbry (1934, p. 59) divided the genus into three sections, Drepano- 

 trema proper, Fossidorbis Pilsbry, and Platytaphius Pilsbry. In the writer's 

 opinion, the last section should be regarded as a separate genus until the 

 type has been dissected and its anatomy made known. The other groups 

 divide the genus Drepanotrema into two comprehensive subgenera. 



Subgenus DREPANOTREIVIA Fischer et Crosse, 1880 



Spire on the right side, narrow and deeply sunken; periphery broadly rounded (type 

 Drepanotrema anatinum (Orh. )= Planorbis yzabalensis C. and F. (Pilsbry) 



Species Considered as Valid. 



Drepanotrema aruitiniun (Orbigny) Drepanotrema chittyi Aguayo 



Plate 79, figs. 16-18 Drepanotrema parapseide (Orbigny) 



Drepanotrema lucidmn (Pfeiffer) Plate Drepanotrema ahenum H. B. Baker 



78, figs. 11-13 Drepanotrema castaneonitens (Pils. 



Drepanotrema hoffniani F. C. Baker and Van.) 



Plate 78, figs. 14-16 Drepanotrema melleum (Lutz) 



Subgenus FOSSULORBIS Pilsbry, 1934 



Having a wide spiral on the right side, very slightly concave; the periphery from 

 rounded to carinate. Type Drepanotrema cultratum ((Drb.) Pilsbry. 



Species Considered as Valid. 



Drepanotrema (Fossidorbis) cultratum Drepanotrema (Fossulorbis) cimex(M.ori- 



(Orbigny) Plate 78, figs. 17-19 cand) 



Drepanotrema (Fossulorbis) c. anitense Drepanotrema (Fossulorbis) c. pistiae 



(Cooper) H. B. Baker 



Drepanotrema (Fossulorbis) c. duenasi- Drepanotrema (Fossulorbis) depressissi- 



anum (Tristram) mum (Moricand) 



Drepanotrema (Fossulorbis) c. labrosum Drepanotrema (Fossulorbis) kermatoide 



Pilsbry (Orbigny) 



Drepanotrema (Fossulorbis) c. panuco Drepanotrema (Fossulorbis) sumichrasti 



Pilsbry (Crosse and Fischer) 



Remarks. Drepanotrema differs in its genitalia and radula from all 

 other American groups of Planorbidae. By its prostate, the diverticula 



