/. CRUSTACEA: CUMACEA. 



-t37 



Indies, which is said to climb palm trees for the cocoanuts, which it eats. 

 Its respirator}' organs have been referred to on p. 432. 



Sub Order 11. BRACHYURA. Body depressed; abdomen rudimentary 

 and folded in a groove under the cephalothorax; antenna short; never 

 more than one pair of feet chelate; ventral nerve cord concentrated (fig. 

 441). Omitting some inconspicuous groups like the porcellain crabs (PoR- 

 cellaxid.e), the IIippid,^, and the Lithodid^, which are united as a group 

 of Schizosomi from the fact that the last thoracic segment is free from the 

 carapace and its appendages are rudimeutary, the sub order is usually 

 divided as follows: LEUCOSOIDExl (Oxystomata). Body oval ortriangular, 

 area of mouth parts triangular, the apex anterior. Calappa, Matuta* 

 Hepatus* ot vcurmer sens. OXYRHYNCHA (Maioidea). Cephalothorax 

 triangular, narrowed in front; mouth area (as in the following tribes) 

 quadrilateral. Mostly tropical. Hijas,* Lihinia* Piigettia* spider crabs. 

 CYCLOMETOPA. Body broader than long, regularly arcuate in front. 

 Cancrid.e, with last pair of feet pointed. Cmicer* shore crab; Pano- 

 peus* mud crab. Portunid.e, with last pair of feet flattened paddles. 

 Platyoniehus *; Neptuiius hastatus,* when thin-skinned after molting, is the 

 'soft-shell crab' of the markets. CATOMETOPA. Front of carapace 

 nearly straight; body from above nearly quadrilateral; Oelasimus,'* the 

 iiddler crabs of our warm shores; Pinnotlieres ostreum,* common in 

 oysters; Gecarcinid^e (f7ca, etc.), land crabs of the tropics, which only go 

 to the sea at the reproductive season to lay their eggs. 



Order IV. Cumacea. 



Small marine forms with sessile eyes, three or four free thoracic somites; 

 appendages biramous; a brood sac beueatb the cephalothorax. Of interest 

 because combining arthrostracan and thoracostracan features. Diastylis 

 (fig. 446). 



Fig. 447. — Diastylis quadrispinosus. 



Especial interest also centres in the little known Aiiaspides tasmanice 

 from lakes in Tasmania, which unites schizopod and amphipod characters. 

 It has the stalked eyes, caudal fin, and biramous feet of a scliizopod; 

 otocysts in the antennute like a decapod; but agrees with the amphipods 

 in shape of body and in free thoracic segments. The epip(jdial plates 

 are paralleled elsewhere only in carboniferous species, with which these 

 forms apparently are closely allied. 



