308 ORTMANN — DISTRIBUTION OF DECAPODS [April 3, 



2. Subgen. Pseudothelphusa Sauss. (= genus Pseudothel- 

 phusa Rthb.). 



3. Subgen. Rathbunia Nobili (= genus Nobili and Rathb.). 

 Genus Kings ley a Ortm. 



It is entirely a matter of taste whether one prefers to regard 

 Potamocarcinus , Pseudothelphusa and Rathbunia as genera or sub- 

 genera. This much, however, is evident, that they are much more 

 closely allied to each other morphologically than to either Epilobo- 

 cera or Kingsleya. Judging from the third maxillipeds (which 

 furnish a good criterion in this respect), Epilobocera should be re- 

 garded as the most primitive form, Potamocarcinus (in the largest 

 sense) would be typical and Kingsleya the most specialized. 



This division into three genera corresponds well to the geographi- 

 cal distribution of the different forms (see Rathbun, 1898, pp. 



532-537)- 



Epilobocera contains six species which are restricted to the Greater 



Antilles: Cuba, Isle of Pines, Hayti, Porto Rico and Santa Cruz 

 Island. 



Potamocarcinus (in the widest sense) contains 47 species 1 , which 

 cover the whole continental range of the subfamily from Mexico to 

 Bolivia and Pará, the Lesser Antilles and of the Greater Antilles, 

 Cuba and Hayti. The subgenus Pseudothelphusa has the same 

 range, while of the two species of Potamocarcinus (sens, strict.) 

 one is found in Guyana, the other in Costa Rica. Rathbunia is 

 known only from Darien. Kingsleya is so far known only from 

 Guyana. 



The range of the subfamily on the continent seems to be perfectly 

 continuous ; only P. agassizi from near Pará appears to be more or 

 less isolated. The most closely allied forms to this one (reflexi- 

 frons Ortm. and denticulatus M.-E.) are found in the region of 

 the upper Amazonas and in Guyana respectively, so that this 

 locality (Pará) is possibly connected with Guyana. There is, how- 

 ever, the other possibility, that along the course of the Amazonas 

 river a connection exists between its lower part (Pará) and its 

 upper (upper Amazonas). A very important fact is that Pará is 



1 Forty-two species mentioned by Rathbun, one described subsequently by 

 Doflein (1900, P. principessce, Colombia), one described by Nobili (1901, P. 

 caputii, Ecuador) ; these forty- four belong to Pseudothelphusa. Two species 

 belong to Potamocarcinus and one to Rathunia. 



