1905.] 



ORTMANN — AFFINITIES OF CAMBARUS. 109 



and a rather long or moderate acumen. The carapace is of normal 

 shape, oval and depressed ; the areola uniformly rather wide, and 

 there is no tendency to become narrow. There !are, however, 

 some differences in length : generally, the areola is about half as 

 long as the anterior section of the carapace (inch rostrum); but in 

 certain species (erichsoni and forceps) it is slightly, and in one 

 species (spinosus) decidedly shorter, and in two others (nistieus 

 and medius) it is decidedly longer. The chelse in this section'are 

 also rather uniform, but not very primitive : they are more or less 

 broad and ovate. The fingers (in old males) generally are gaping 

 at the base, and in contact distally, and the movable finger pos- 

 sesses a peculiar S-shaped curve. The immovable finger is generally 

 not bearded at the base (a slight indication of a beard is seen in : 

 C. propinquus, obscurus, neglectus). In C. forceps, the fingers are 

 unusually and widely gaping, up to the tips. In C. medius the chelae 

 are unusually broadly ovate, and the movable finger has no S-curve. 



The annulus of the female is flat, with a median depression and 

 raised margins. Very often the anterior margin is elevated into 

 tubercles, and in C. hylas the posterior margin is very prominent, 

 which is rather unusual in this section, and ought to be confirmed 

 by additional investigations. 



This section contains ten species, which may be divided into two 

 groups. 



1. Group: {propinquus). 



Tips of sexual organs comparatively short, reachitig only to the 

 third rarely {in erichsonianus) to the second pereiopods, without or 

 with {obscurus) a shoulder on the anterior margin. Outer tip regu- 

 larly tapering from base to end. 



2. Group.- {rusticus). 



Tips of sexual organs long, reaching rarely only to the second, gen- 

 erally to. the first pereiopods, mostly with a shoulder on the anterior 

 margin. Outer tip not regularly tapering, but thin {setiform) from 

 base to end. 



C. erichsonianus forms a transition between the two groups : the 

 sexual organs are rather long, but they lack a shoulder, and in shape 

 they resemble those of C. propinquus. 



3. Section : C. virilis. 



Sexual organs generally quite long {rarely rather stout), reaching 

 about to the second pereiopods, deeply split at the tips, tips slender 



