CRUSTACEA MALACOSTRACA. 



I. PODOPHTHALMATA. 



Malacostraeous Crustacea with stalked eyes, mandibles and 

 maxillae adapted for mastication, and a dorsal shield or carapace 

 covering the whole or the greater part of the dorsal and lateral 

 regions of the thorax. 



Order DECAPODA (EUBRANCHIATA). 



Branchiae enclosed in a branchial chamber formed by the 

 lateral portions of the carapace. 



Tribe BEACIIYUBA. 

 Abdomen short, inflexed beneath the thorax, without swim- 

 merets, and with no appendages on the penultimate segment. 

 Carapace greatly developed, forming wide branchial chambers 

 . above the bases of the legs. Sternum never linear ; vulvas situated 

 on the sternum. Antennae with the flagella usually very short, 

 especially those of the inner pair, which are lodged in distinct 

 cavities. External maxillipedes operculiform. Buccal cavity 

 distinctly defined in front. 



Sub-Tribe Oxtehtncha. 

 Carapace more or less narrowed and rostrate in front ; the 

 branchial regions greatly developed, the hepatic regions rudimen- 

 tary. Branchias nine in number. Internal antennae longitudinally 

 plicate. Epistome usually broad. Buccal cavity sub-quadrate ; 

 efferent canal from the branchiae terminating at the sides of the 

 jjalate. Eourth joint of the external maxillipedes inserted at 

 the summit or at the antero-internal angle of the third joint. 

 Male genital appendages inserted in the base of the fifth pair 

 of legs. 



