20 U.S. NATIONAL MUSEUM BULLETIN 292 



The monotypic Jonga and Micratya are each known with certainty 

 from only five islands in the AntUles: both occur on Cuba, Jamaica, 

 Puerto Rico, and Dominica; the former is found also on Barbados, 

 and the latter on Martinique. We have several specimens of Jonga 

 and a single female of Micratya that were collected in Costa Rica 

 and that may be conspecific with the West Indian species; these 

 records should not be accepted for the species, however, until ad- 

 ditional specimens become available for comparison. In view of the 

 apparent absence of the two from the lower islands in the Lesser 

 Antillean chain and in South America, we are inclined to consider 

 that they reached the Greater AntUles from the Central American- 

 Mexican region and spread southeastward. 



While three species of the genus Potimirim occur in the West 

 Indies, only P. americana is endemic (Cuba, Jamaica, and Trinidad) . 

 Potimirim mexicana ranges from northeastern Mexico to Costa Rica 

 and occurs on Cuba, Jamaica, and Puerto Rico. Potimirim glabra is 

 reported here from the Antilles for the first time, having been found 

 on Dominica; elsewhere it occurs in Central America and Brazil. 

 The interrelationships of the members of the genus are somewhat 

 enigmatic, and whUe the probably primitive branchial characters 

 of P. americana and P. glabra bring them closer to each other than 

 to either of the two remaining species of the genus, P. mexicana and 

 P. potimirim (from Brazil), the characters of the appendix masculina 

 places them at opposite extremes. Even with the apparent discon- 

 tinuities in the ranges of the West Indian species and the puzzling 

 occurrence of P. americana (instead of the expected P. glabra) on 

 Trinidad, one is inclined to assume that the ancestors of P. americana 

 arrived in the Greater Antilles from the Central American-Mexican 

 region and subsequently migrated southward along the Lesser Antil- 

 lean chain. The invasion of the Antilles by P. mexicana from the 

 same region and by P. glabra from South America along the Lesser 

 Antilles probably occurred at a later time. Such an assumption'is 

 supported by a comparison of the appendices masculinae of the four 

 species: that of P. americana consists of a simple subcircular lobe; 

 in P. mexicana it is more elongate, and the posterior border is very 

 shallowly trilobate; in P. potimiriin it is even more elongate, and the 

 three lobes more distinctly delimited; and in P. glabra the pattern is 

 quite similar to the latter but with a deep, rounded, naked sinus 

 between the proximal two lobes. There can be little question, on the 

 basis of this character, that P. americana has its closest affinities with 

 P. mexicana and that P. potimirim links the latter with P. glabra. 



The genus Typhlatya is represented in the Antilles by two species, 

 T. garciai (Oriente Province, Cuba) and T. monae (Isla Mona and 

 Barbuda) and a third species, T. pearsei Creaser, occurs in Yucatan. 



