WATERLIME GROUP. 397 



The diflFerent species of this genus present some slight modifications in general 

 form and in the appendages. The feet are all surrounding the mouth, and belong 

 to the cephalic portion of the animal. The anterior feet are nine-jointed, including 

 the terminal articulating spine : the first joint is narrow at its base and spreading 

 above, and the second joint is longer than the others. In the three anterior pairs, 

 the distal extremities of several of the articulations preceding the last one have 

 a slender spine on each side ; but this character may perhaps be varied by ori- 

 ginal conformation, or bj' accident. The dilated portion of the first joint is in- 

 tended to aid in the process of manducation, and may have been serrate. 



The accompanj'ing diagram is an enlarged figure of one of the third pairs of 

 feet. 



Fig. 1. 



In the arrangement of these appendages, the part a of the second joint is covered 

 by the next one behind it as far as the oblique line limiting what appears to be a 

 flattened portion of the joint. A part of the first joint h was, in like manner, co- 

 vered by the next posterior one. 



The fourth pair, which are more slender than the others, with longer joints, 

 have shown no spines except on the penultimate, and the last joint is itself a 

 slender spine. 



The fifth or swimming feet are eight-jointed, with a terminal palette*. 



Fig. a. 



,1 ^^ 4 , $ , 



» 



The figures refer to the number and relative position of the successive joints of 

 the natatory feet 



At t the margin is serrated, as mentioned in the description above. 



At the line s there is a soldered suture, connecting the fixed ramus of the chela 

 with the penultimate joint. In some specimens the parts have been separated along 

 this line. 



• Id indicating tiie number of joints, I liave been governed by no theoretical views, but simply by tlie 

 appearances of separation in the parts; and though the two extremities of the third joint, as marked, show 

 no articulating processes, the limitation of the parts is distinct, and they may have been separated only by 

 ft thin extension of the cbitine, and may not be properly articulating surfaces. 



