EXTRACTED FROM THE AMERICAN JOURNAL OF SCIENCE AND ARTS, VOL. XII. 
- SECOND SERIES, JULY, 1851. 
d ! ON THE T " 
CLASSIFICATION 0F THE CANCROIDEA. 
Bx JAMES D. DANA. 
bo 4 
Tur Caneroidea (or Crustacea Cyclometopa), like the Maioidea, are 
characterized by having, (1) the branchie 9 in number, 7 of which 
lie so as to form the exterior of the branchial pyramid ; (2) the efferent 
passage from the branchial cavity passing over the lateral portions of the 
palate ; (3) the male genital orifices situated in the base of the posterior 
legs and covered by the abdomen ; (3) the male abdomen not narrower 
at base than the corresponding part of the sternum ; (4) the buccal 
area subquadrate, and the 4th joint of the outer maxillipeds articulated 
with the 3d by its inner angle. "The Telphusidze have these characters, 
and may be considered true Cancroidea, though approximating to the 
Grapsoidea in the large vacant space in the branchial cavity, and having 
some peculiarities in the branchie fitting them for freshwater life. 
'The Corystes group also partake of the Cancroid character; yet they 
diverge from it, in the large outer antennz; more or less hairy, and 
both in this respect and in form, they approach the Hippa group, and 
thus have a much lower position in the series than the Cancroidea. 
They have no true relation in the character of the buccal area and 
efferent canal to the Leucosia group. 
The genera Acanthocyclus and Corystoides (of Lucas) have the gen- 
ital orifices, sternum and abdomen, and outer maxillipeds of the Can- 
croidea and Corystoidea ; but the branchic (in Acanthocyclus at least) 
SECOND BxnrES, Vol. XIT, No. 34.—July, 1851. 18 Ü 
[ 
^T 
