12 ASTACID^. 



1858. Mr. H. de Saussure, in Mem. de la Soc. Phys. de Geneve, T. 14, 

 Pars II., pp. 456-461, Tab. III. f. 21-23, gives detailed descriptions 

 and figures of the three before-mentioned species. His remark, that 

 the Cambams prefer the marshes and muddy waters, is apparently not 

 of general value. Many species of Cambams, perhaps the greater part, 

 live in pure running water ; for some species it is directly stated by Dr. 

 LeConte. 



I find it impossible to separate the species described by Mr. De Saus- 

 sure from the species described by Mr. Erichson, but a judgment from 

 two descriptions (I have seen only one female) is always doubtful. I 

 am not sure that the hooked legs described by Mr. De Saussure corre- 

 spond with those of Mr. Erichson. I think Mr. De Saussure's second and 

 third pairs of legs are the third and the fourth of Erichson, the latter 

 commencing the numbering of the legs with the great claws, Mr. De 

 Saussure beginning with the pair next after the great claws. I think 

 the words in the Note by G Montezuma?, "son G. Mexicanus en est 

 bien distinct par le troisieme article inerme de la quatneme paire des 

 pattes," is otherwise not intelligible. In C. consobrinus the second joint 

 of the legs is said to be hooked ; if this be not a typographic error, it 

 is a strange exception. 



G. consobrinus is not at all compared with G Cubensis Erichs. ; per- 

 haps it is unknown to Mr. De Saussure. The two descriptions show no 

 difference. The lamina of the antennae, f. 21, b., has no apical external 

 spine, — perhaps an error. 



G Montezuma? does not differ from G Mexicanus, and G. Aztecus seems 

 identical with G Wiegmanni. But I confess that my materials are too 

 imperfect to decide this question. 



ON THE CONSTANCY OF THE SPECIFIC CHARACTERS 



AMONG ASTACID^E. 



The examination of the constancy of the specific characters was a 

 chief point in my labor, especially because Mr. Gerstfeldt, in his excel- 

 lent monograph concerning the fresh-water Crustacea of Europe, has 

 reduced the number of described species to only two, by proving that 

 the characters relied on in their separation are far from being constant. 



The exceedingly rich mass of material before me, thus far unrivalled 

 for such a labor, has permitted a very extensive and careful examina- 

 tion of the constancy of the characters. Otherwise viewed, it could not 

 be denied that this rich material — there being more than a hundred 

 specimens of some species — Avould rather serve to obstruct the judg- 

 ment of the worker. 



Dr. J. Le Conte, in his careful monograph of the Astaci of Georgia, 

 says : " The shape of the rostrum and of the chelte and the size of the 



