ox CRUSTACEA. 259 



the root of the feet, under the lateral and inferior jut of the 

 carapace. They repose upon two solid, oblique tables, of the 

 interior of the body, which serve to close the lodges above, 

 where the first muscles of the feet are fixed. The water can 

 penetrate to them through a cleft which is behind this edge of 

 the carapace, and issue out through an anterior aperture situ- 

 ated near the mouth. In one genus, that of Dorippus, this 

 anterior aperture, pierced in the body itself of the carapace, is 

 very remarkable : their gills have each the form of a triangular 

 pyramid, elongated, attached only by its base, and with the 

 point directed upwards and inwards. They are composed of 

 a stem of a cartilaginous nature, supporting numerous soft 

 and membranaceous laminae, separated into two longitudinal 

 masses by a medial furrow, and piled one upon another, per- 

 pendicularly to the axis of the stem which sustains them. In 

 the furrow ai*e found two thick vessels, one venous, the other 

 arterial, which distribute their branches ad infinitum o\%x the 

 surface of the membranaceous and double laminae of the gills, 

 so that the lymph there receives the impression of the respi- 

 rable air mixed in the water. 



These gills are seven in number on each side, five depend- 

 ing on the feet properly so called, and two on the first and se- 

 cond jaw-feet. They are continually rubbed by two long thin 

 cartilaginous and flexible laminae, attached near the base of the 

 jaws, one above, the other underneath these organs ; and the 

 function of which appears to be, as M. Cuvier presumes, to 

 express the water, which has served for respiration, from the 

 intervals of the leaflets of the gills, so as to allow fresh supplies 

 to enter. 



The gills of the decapod macrourous Crustacea differ from 

 those of the brachyin-i, in that the leaflets or respiratory 

 laminae are replaced by cylindrical filaments, disposed in tufts, 

 which have each a vein and an artery. They are also much 

 more numerous, being twenty-two on each side, divided into 



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