438 CRUSTACEA [November, 



as long as the body, with short rigid hairs, interiores con- 

 cealed; feet concealed, anterior pair near the base of the 

 thorax and dilated at tip, posterior pair at the origin of the 

 tail, extended obliquely, prominent, dilated, bisetous at tip; 

 abdomen^ basal segments very short, transverse, each side 

 reflected, curvilinearly narrowed without interval, termi- 

 nal segment longer, semiorbicular, narrower than the pre- 

 ceding ones and concealing the first caudal segment; tail 

 half as long as the body, abruptly narrower than the pre- 

 ceding segment, segments three, basal one longitudinally 

 quadrate, largest, second one transversely quadrate, nar- 

 rower than the first in the female, elongated and attenuated 

 in the male, third segment bifid and bisetous at the tip. 



Length one fortieth of an inch, male smaller. 



Cabinet of the Academy. 



I have placed this parasite in GeofFroy's genus Bino-' 

 cuius y not in consequence of the particular definition of 

 that genus, but from a general resemblance in the outline, 

 and similarity in the number and proportion of the seg- 

 ments of the body, which it imquestionably bears, to the 

 singular animal dicovered by that author, now the type 

 of the genus. 



In these two animals there are however striking dis- 

 similarities, which it is unnecessary here to particularize, 

 as those who are conversant with the generic characters 

 as laid dow^n by Mr. Latreille, will immediately perceive 

 them by the above description. 



This parasite was found in considerable numbers, on 

 various parts of the body of the specimen of Callianassa^ 

 described on page 238 of this Journal. The two sexes 

 of nine tenths of the specimens were in coitu, the male 

 adhering to the tail of the opposite sex, so as to conceal 



