118 ORTMANN— AFFINITIES OF CAMBARUS. 



[April 13, 



nulus of the female is, corresponding to the uniformity of the male 

 organs, also very uniform, and is characterized by its posterior ele- 

 vation. Aside from the length and width of the areola, the shape 

 of the chelae, the presence or absence of marginal spines of the 

 rostrum, and the shape of the carapace serve to distinguish the more 

 primitive forms from the more highly developed, and furnish a 

 division of the subgenus into sections as follows : 



1. Section : C. hamitlatus. 



Carapace subcylindrical. Rostrum with or without marginal 

 spines. Chelce long, subcylindrical. Areola rather long. Eyes 

 rudimentary. 



Only two species, C. hamulatus and setosus, belong here, both 

 blind cave-forms. They do not seem to be closely related to one 

 another, since they differ in very important characters. The sub- 

 cylindrical shape of the chelae, however, indicates, that both are 

 rather primitive, and have become separated from the primitive 

 stock of this subgenus very early, and probably independently. 

 The shape of the carapace, the long areola, and the rudimentary 

 eyes are very likely due to parallel development, brought about by 

 the similar conditions under which these species are found. (See 

 Faxon, Pr. U. S. Mus., v. 12, 1890, p. 628). 



2. Section : C. extrancus. 



Carapace more or less ovate, depressed, with lateral spines behind 

 cervical groove. Chela not very elongated, depressed, and rather 

 broad, but a little more elongated than in the following sections. 

 Areola more or less wide, of medium length, about half as long as 

 anterior section of carapace, sometimes slightly shorter, rarely, in C. 

 cornutus, the areola is rather long. Eyes well developed. 



Two of the species belonging here ( C. extraneus and jordam) 

 are typical, and are unquestionably the most primitive forms of the 

 subgenus, as is shown by the shape of the carapace, the rostrum, 

 and chelae, at least as compared with the following sections. The 

 third species, C. cornutus, stands by itself, and is a rather aberrant 

 form, peculiar on account of its antennae, which have a large, com- 

 pressed flagellum, ciliated on inner margin. Also the spines of the 

 rostrum (upturned) are peculiar. In the long areola, it is rather 

 advanced. It seems to be a peculiar local form, developed out of 

 the primitive stock now represented by C. extraneus and jordani, 

 and we may safely leave it with this section, since the only alter- 

 native would be to create for it a separate section. 



