1902.] AND ANCIENr GEOGRAPHY. . 309 



the only locality known for this subfamily to the south of the Ama- 

 zonas river, at least in Brazil. Generally, we may call this river 

 the southern boundary of the range of the subfamily, although in 

 the Cordilleras of Peru and Bolivia Potamocarcinince are found more 

 to the south. 



The localities of this subfamily in the West Indian islands are 

 now separated from the main range on the continent. Here we 

 can distinguish two groups : the Greater Antilles possess as a charac- 

 teristic type the genus Epilobocera, which is found nowhere else. 

 At the same time we have in Cuba three species of Pseudothelphusa , 

 of which one (americana) is also found in Hayti. This same spe- 

 cies, P. americana Sauss., is found largely distributed in Mexico 

 (States of Guanajuato, Morelos, Puebla, Guerrero, Oaxaca), and, 

 further, another Cuban species (terrestris Rthb.) has also been 

 reported from Mexico (Jalisco and Tepic), while the third species 

 (affinis Rthb.) is restricted to Cuba. 1 



The second group within the West Indies is formed by the islands 

 of Gaudeloupe, Dominica, Martinique, St. Lucia, where one species 

 (jP. dentata (M.-E.)) is found. According to Rathbun (1898, p. 

 524), the most closely allied forms to this are P. gar??iani Rthb. 

 from Trinidad and Venezuela, and P.fossor Rthb. from Venezuela. 



The above chorological and systematic facts justify the following 

 conclusions : 



1 . The distribution of the Potamocarcininoz in Central and South 

 America is remarkable, in so far as it does not go southward beyond 

 the Amazonas river. 



2. The West Indian islands must have been once connected with 

 Central and South America. The freshwater crabs of the Greater 

 Antilles point to a connection with Mexico, as well as to a connection 

 between themselves, after they were separated from the mainland 

 {Epilobocera). The freshwater crabs of the Lesser Antilles point 

 to a connection with Trinidad and Ve7iezuela. 



Connection of the Polamocarcinin.ee and Potamo?iince. 



As is accepted by all authors, the affinity of the Potamocarcininoz 

 of the New World with the Potamonince of the Old World is 

 beyond question, and this affinity is expressed by their position as 



1 This locality, given for a specimen from the old collection of Guérin in 

 Philadelphia, needs confirmation. 



