122 



E. A. ANDREWS. 



without mention of the annulus ; subsequently Martens (6) de- 

 scribed a variety and Faxon (7) gave a new account of the 

 typical form, of which he says the annulus " is movable, fixed 

 only at the posterior end, between the sterna of the penultimate 

 and last thoracic somites. The ventral face of the annulus is 

 marked by a longitudinal fossa open at the posterior end " (page 

 122). Several varieties of the species were later briefly de- 

 scribed by the same author (8). Recently Ortmann has exam- 

 ined the specimens of Mexican crayfishes from the Paris Museum 

 (2) and mentioned in a footnote that the peculiar spine posterior 

 to the annulus in his new subgenus ParacambariLS distinguishes 

 this from all other Cambari except C. montezumce. 





Fig. 1. 



The above is all thus far known regarding the annulus in 

 Cambarus montezumce, or in the subgenus Cambarcllus , in which 

 it is placed by Ortmann. 



