CRUSTACEA. 547 



subservient to locomotion. Each of these legs supports at 

 the base, but concealed from view, a pyramidal plumose 

 gill. This position of the gills induced Lamauk to deno- 

 minate the section Homohranches. In many species, the 

 anterior pair of locomotive feet are large, and the last joint 

 of the tarsus furnished with a forceps (cheliferous). In 

 some of the species the jjosterior feet are broad, and fitted 

 for swimming. The tail consists of several joints, is fur- 

 nished beneath with several pair of fringed filaments for the 

 retention of the eggs, and, in some, vrith terminal plates for 

 swimming. 



Tribe I. — Podophthalma. 



Eyes pedunculated. 



A, Brachyuua. Tail short and simple at its extre- 

 mity, and incurved upon the abdomen. 



Dr Leach, whose labours qualify him, in a peculiar 

 manner, for arranging crustaceous animals, has given a me- 

 thodical distribution of the genera of this group, which we 

 shall here insert *. 



a. Abdomen of the male Jive jointed, the middle joint 

 longest ; of the female seven jointed. Anterior pair of legs 

 didactyle. 



Division I. Shell (shield) nearly rhomboidal. Two 

 anterior legs very long, with deflexed fingers. 



1. Lambrus. 



Division II. Shell truncate behind. Two anterior legs 

 of the male elongate, of the female, moderate. 



Subdivision 1 . Antennas long, ciliated on each side. 



• Article Annulosa in the Supplement to the Encyclopsedia Biitannica, 

 likewise published in " The Entomologist's Useful Compendium," by 

 George Sajiuelle, 8vo. London, 1819, — a work which gives many conve=. 

 nient indications of the British npecies, 



M m 2 



