ASTACIDEA. 5^5 



beyond beak, very slender ; the flagellum reaching as far forward as 

 the anterior legs. The large hand is longer than twice its width. 

 Either side of the beak there is a slight ridge running longitudinally 

 for a short distance from the front edge. The postero-lateral piece of 

 the carapax has the anterior margin denticulate. The postero-dorsal 

 piece is subacute behind, and has two distinct transverse sutures, 

 besides another more anterior less distinct. 



Subtribe II. ASTACIDEA. 



The division Astacidea is identical with the "Familia Macroura 

 Astacina" of De Haan, in its extent and subdivisions, except that we 

 exclude the Thalassinidea, which De Haan places in the same sub- 

 division with Astacus, and we do not add the Megalopidea, as they 

 appear to have closer relations with the Anomoura. The following 

 are the families adopted : 



1. Antennce external squama basalt non instructs. Pedes antici monodactyli. 



Fam. I. Scyllarim. — Carapax valde depressus, marginibus laterali- 

 bus sat tenuibus, carapace lateraliter subito inflexo. Antennse 

 externaa laminatae, breves. Sternum trigonum. 



Fam. II. Palinuridje. — Carapax subcylindricus, lateraliter late ro- 

 tundatus. Antennae externse basi subcylindricae, longae. Sternum 

 trigonum. 



2. Antenna external squamd basali instructs. Pedes antici didactyli. 



Fam. III. Eryonim. — Carapax non oblongus, depressus, lateribus 

 subito inflexis, abdomine multo angustiore. 



