NO. 1158. FRESH WATER CRABS OF AMERICA— BATHBUN. 531 



The second group, with quadrate meri, embraces E. haytensis and 

 JE. sinuatifrons {E.portoricensis, manuscript, Berlin Mus,). E. haytensis 

 is much flatter than any other member of the g,enus, and is narrower 

 than sinuatifrons^ with strikingly larger eyes and strongly ])rotruding 

 inferior frontal margin; this margin is not visible in a dorsal view of 

 sinuatifrons. 



ANALYTICAL KEY TO THE SPECIES OF EPILOBOCERA. 



A. Froiit without superior crest; esognath considerably overlapping merus of 



endognath ; spine of efferent channel narrow {/ilmanii 



A . Front with superior crest; exognath slightly overlapping merus of endognath ; 

 tooth of etiereut channel short and hroad. 

 B. Merus of endognath broad, its outer and anterior margin arcuate. 

 C Width varying from 1.56 times the length iu small specimens to 1.64 times 

 the length in large .specimens. 



D. Anterolateral teeth spiniform armata 



D'. Autero-lateral teeth dentiform cubennia 



C. Wider; width of small specimens 1.7 times length yranidata 



B'. Merus of endognath narrower, subfinadrate, with an antero-external angle. 



C. Inferior margin of front projecting beyond the superior haytensis 



C . Inferior margin of front not projecting beyond the superior sinuatifrons 



RATHBUNIA Nobili. 



Rathiunia Nobili, Boll. Mus. Zool. Torino, April 16, 1896, XI, No. 238, p. [1] ; 

 March 15, 1897, XII, No. 280, p. [2], text figure. 



This genus is allied to Pseudothelphnsa, but differs from it and also 

 from all other members of the subfamily iu the form of the outer 

 maxilliped (see text figure cited above), the merus of which is very 

 narrow posteriorly. Its posterior margin is articulated with the outer 

 half of the anterior margin of the ischium. 



The genus was founded on a single specimen (female) from Darien, in 

 the museum at Turin, Eathhunia festcc. It is one of the largest of the 

 Pseudothelphusiuai, being equaled only by Pseudothelphnsa magna and 

 henrici, Potamocarcinus nicaraguensis, and Epilohocera sinuatifrons. 



DISTEIBUTION OF THE PSEUDOTHELPHUSIN^. 



The genus Epilohocera, with six species, is confined to the West 

 Indian Islands. 



The genus Potamocarcinus, with three species, is continental, so far 

 as known, ranging from Nicaragua to Guiana. 



The genus Rathhunia, one species only, inhabits Darien. 



The genus Pseudothelphnsa embraces many more species than any of 

 the above, and ranges throughout the West Indies and on the continent 

 from the States of Jalisco and Guanajuato in Mexico to Peru and 

 Bolivia on the west, and Para, Brazil, on the east. There is no indis 

 putable evidence of its occurrence in Chile. The Potamonidiii are rep- 

 resented in Brazil, Argentina, Paraguay, Uruguay, aud Chile by the 

 TrichodactyliniV, which, however, are not confined to those countries, 

 but inhabit nearly the whole of South America and extend into iSica- 



