142 CRUSTACEA. 



widens much below on its outer side, and where this side terminates 

 adjoining the orbits, there is a small fissure in the orbital margin. 

 The second and third joints are small and nearly cylindrical. The 

 flagellum is about fourteen-jointed. On the upper side of the orbit 

 there is another small fissure, which furcates a short distance above 

 and passes either side of a triangular piece, which is free at summit. 



The anterior legs are wholly unarmed ; the fingers are pointed and 

 very finely and 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 swimming and the 

 gressorial species; and the subdivisions Cancrinea and Portunima 

 corresponding to this distinction, are those ordinarily adopted. These 

 are the only groups of this grade adopted by Edwards or M'Leay. 



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.) Cryptopoda, including CEthrus. 



(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, Ruppellia, 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 " Canceriae" into three families, 



