1905.] ORTMANN— AFFINITIES OF CAMBARUS. Lia, 
This section is formed to receive an isolated species, the position 
of which seems quite uncertain. There is a remote resemblance of 
the sexual organs to those of C. dffictlis of the third section of this 
subgenus, and in other characters there are resemblances to C. mzs- 
stssippiensts, namely in the lack of marginal spines of the rostrum, 
and in the obliteration of the areola. The annulus of the female 
agrees with C. faldmert in being depressed in front, and prominent 
and tuberculated behind: but a similar shape is found in the sub- 
genus Bartonius. On the other hand, also the male sexual organs 
can be compared with Aarfonius, although they are by no means 
identical with the very uniform type seen in the latter subgenus. 
The chelz, according to the description, are very peculiar, namely 
long and subcylindrical, the palm with subparallel margins: this is 
entirely unlike anything that is seen in the wirz/7s-section of the 
present subgenus, and rather stamps this species a primitive one. 
Then, again, this species presents in the elongate rostrum and 
antennal scale very unusual features. 
Thus it is hard to form a positive opinion about its position. I 
should not hesitate to place it with the palmeri-group of the virzlis- 
section, if it was not for the primitive character of the chele. Ac- 
cording to the latter, and possibly also according to the sexual 
organs, we might place it at the beginning of the subgenus, as a 
peculiarly developed primitive form, but it also may be the most 
highly specialized form of the subgenus. The distribution (Mis- 
sissippi and northeastern Arkansas) would fit either assumption. 
KEY TO THE SPECIES OF THE SUBGENUS FAXONIUS. 
1. Section of C. limosus (see p. 108). 
a, Generally third and fourth pereiopods with hooks in the male. Carapace sub- 
cylindrical, Areola wide and long. Chelz subcylindrical. Eyes rudi- 
mentary. C. (Faxonius) pellucidus (Tellk. ). 
a, Only third pereiopods with hooks in the male. Carapace ovate, depressed. 
Areola rather wide, of medium length (about half as long as anterior 
section of carapace). Chelze not subcylindrical, compressed, and more 
or less ovate. Eyes well developed. 
6, Sexual organs thick, swollen in the middle, tips short and stout, both 
slightly curved in the same direction. C. (faxonius) harrisont Fax. 
4, Sexual organs short, thick, but not swollen, straight. Tips divergent. 
¢, Sides of carapace with one spine behind the cervical groove. 
d, Sexual organs with tips not crossed, the outer directed outward, 
the inner inward. C. (Faxonius) sloanet Bund. 
