356 CLASS CRUSTACEA. 



pair of feet. The others are more solid or corneous, with a 

 range of small spines at the posterior edge ; the last is larger 

 than the preceding, almost square, depressed, angular, and 

 terminated by two filaments or articulated setae. In some 

 species composing the genus Lepidurus of Dr. Leach, we 

 observe in their interval a corneous lamina, flatted, and ellip- 

 tical. If the number of feet is about a hundred and twenty, 

 the last rings, commencing with the eleventh or twelfth, must 

 support more than one pair, which, in this point of view, 

 approximates these Crustacea to the myriapoda. The testa, 

 perfectly free from its anterior attachment, covers a large 

 portion of the body, and thus protects the first segments, 

 which, as we have observed, are of a softer consistence than 

 the following : it consists of a large corneous shell, very 

 slender, almost diaphanous, representing the upper teguments 

 of the head and of the thorax united, and forming a large 

 oval buckler, convex, notched in the manner of an angle, and 

 denticulated at its posterior extremity. It is divided at its 

 upper face by a transverse line forming two united arches, 

 into two areas, the anterior of which, almost semi-lunar, 

 answers to the head, and the other to the thorax. The 

 first presents, in the middle, three simple eyes, or without 

 any sensible facettes, very closely approximated, the anterior 

 two of which are larger, almost in the form of a kidney, and the 

 posterior of which is much smaller and oval. A duplicature 

 of the anterior portion of the testa forms underneath a sort of 

 frontal buckler, flatted, in the form of a half-moon, and serving 

 as a basis to the labrum. The posterior area, that which 

 corresponds to the thorax, is carinated at the middle of 

 its length. This testa is fixed only by its anterior extremity, 

 so that from this point the entire back of the animal may be 

 uncovered. The sides of this shell, viewed underneath, and 

 by the light, present each a large spot, formed of a great num- 

 ber of lines, describing concentric ovals, and which appear 



