CRUSTACEA. 



142 



i i i r* ™ its outer side, and where this side terminates 

 f^t*" Itl small fissure in the orbital margin. 

 3T3? -5 'Sri *L - small and nearly cylindrical. The 

 L el n t about fourteen-jointed. On the upper s.de of the orbrt 

 JS isanother small fissure, which furcates * short d.stance above 

 and Passes either side of a triangular piece, which » free at Bumnnt. 



The an erior legs are wholly unarmed; the fingers are pomted and 

 V er?finTand evenly denticulate. The hand and other joints have 

 a pitted surface. The following legs are alate and angulate on the 



margins. 



II. CRUSTACEA CANCROIDEA. 



In the distribution of the Cancroidea, a division into two groups is 

 obvious on the most superficial inspection,— the mmmmng and the 

 gressorial species; and the subdivisions Cancrinea and Portumnea 

 corresponding to this distinction, are those ordinarily adopted Ihese 

 are the only groups of this grade adopted by Edwards or MLeay. 



Edwards arranges the genera under these divisions without any 

 reference to their higher family relations, and makes for the Cancri- 

 nea the three groups, 



(1.) Cryjptqpoda, including (Ethrus. 



(2.) Arcuata, including Cancer, Xantho, and the allied broad 



species. 



(3.) The Quadrilaterales, including the narrow or quadrate species 



Eriphia, Trapezia and Melia. 



According to this arrangement, RuppeUla, which is closely allied to 

 Eriphia, is placed in the second subdivision; and Cancer, which is 

 peculiar in its longitudinal inner antennae and narrow front, falls 

 between Etisus and Pilumnus. The arrangement is in fact, simply 

 such as is convenient for a determination of the genera, and not that 

 based on natural affinities ; and this appears to have been the object 

 of its distinguished author. 



M'Leay divides his " Cancerise" into three families, — 



