Procamearus, a New Subgenus. 441 



mm., abdomen, 25 mm., length of hand 13 mm., of pahii 7 mm., of 

 fingers 6 mm. 



The specific name is given in honor of the discoverer, Mr. E. B. 

 Williamson. Before Mr. Williamson started for Guatemala, I called 

 his attention to the possible presence of a Canibarns in this country, 

 and his search was rewarded by the discovery of this species. 



Remarks on the Geographical Distribution. 



The existence of a Caiiihanis in Guatemala (Cohan, Alta Vera 

 Paz) was first mentioned by Huxley (1878), but the species has 

 never been described. It remains doubtful whether the present 

 species is the same, since it comes from another part of the country, 

 although both localities belong to the Atlantic slope. 



Cambariis zvilliamsoni is sharply distinguished from all other species 

 of the genus, although it forms a natural grouj) (subgenus Procambari/s') 

 with three other species, two of which are found in Mexico {digueti, 

 mcxicamis), and the third in Cuba ( ciibi-iisis). The most closely 

 allied form is C. inexicamis, but this is a])|)arently more highly 

 specialized, as is shown by the lack of the marginal si)ines of the ros- 

 trum and the lateral spines of the carapace. Thus C. williainsoni is 

 to be regarded as a rather primitive form, and stands between C. d/'g- 

 i/eti and C. mexicamis. I have regarded C. c/4''^/if// as the most primi- 

 tive form of the whole genus ; but second to it -is C. tvilliamsoui. C. 

 niexicaniis comes very close to the latter, while C. ciibcusis is more 

 remote from the rest on account of the broadly dilated inner face of 

 the male organs ; but the beginning of the development of this feature 

 is clearly indicated in the other three species. 



Thus it is beyond doubt, that C. ciibensis points in its affinities to 

 Guatemala and Mexico, and our Guatemalan species indicates the 

 way by which Cuba was populated. In my paper referred to {Proc. 

 Am. Phil. Soi\, 49, 1905), I have already assumed this connection 

 on the map, without knowing anything of the existence of C. tvil- 

 liamsoui, and this assumption has been fully confirmed by the dis- 

 covery of this species. 



The subgenus Procambants ap]:iears to be the earliest type of the 

 genus, and its range is in the original home of the genus (Mexico and 

 Guatemala), with the exception of C. ciibcusis^ which apparently is 

 an early emigrant. 



The separation of the subgenus Procauibarus from the rest of the 



