CANCROIDEA. 145 



the non-swimming Cancroidea. The true value of this peculiarity in 

 classification, has been remarked upon on pages 71, 72. 



With these characters in view, we distribute the Cancroidea as 

 follows : — 



Legio I. CANCRINEA, vel CANCROIDEA TYPICA. 



1. Pedes postici gressorii. 



Fam. I. Cancridje. — Palatum colliculo utrinque non bene di visum. 

 Carapax saepius late transversus, interdum angustus. 



Fam. II. Eriphidjs. — Palatum colliculo utrinque bene divisum. 

 Carapax saepius angustus, interdum latus, margine antero-laterali raro 

 longiore quam postero-lateralis, latitudine ante-mediana ssepissime 

 longiore, oculis remotis. 



2. Pedes postici natatorii. 



Fam. III. Portunidje. — Ramus maxillipedis lmi internus lobo 

 interno instructus. Palatum saepius colliculo utrinque divisum. 



Fam. IV. Platyonychim. — Ramus maxillipedis lmi internus non 

 lobatus. Palatum colliculis non divisum. 



Legio II. TELPHUSINEA, vel CANCROIDEA GRAPSIDICA. 

 Fam. I. Telphusidjs. 



Legio III. CYCLINEA, vel CANCROIDEA CORYSTIDICA. 

 Fam. I. ACANTHOCYCLIDiE. 



In all the species, excepting some Eriphidae, the orbit has a hiatus 

 at the inner side, which is occupied wholly or in part by the base of 

 the outer antennae, or a process from it. The portion of the Eriphidae 

 alluded to (the subfamily Eriphince), are, in fact, the only examples 

 among the Brachyura in which the orbit is entirely enclosed by the 

 shell, so as to exclude wholly the base of these antennae from forming 

 any part of the circuit. Ruppellia and Eriphia are hence related in 

 a character of prominent importance; and the former of these genera 



37 



