ORDER DECAPODA. 159 



conformed in the usual way. The external jaw-feet present 

 distinctly but three articulations, the first of which is large, 

 transverse and arched, and the last provided at its internal 

 base with a small appendage. The tail of the female is very 

 ample, and covers all the under part of the body. 



AVe now arrive at Crustacea, which, analogous to the last 

 by reason of the insertion of their ocular pedicles, are never- 

 theless remote from them as respects the testa : it has the 

 form of a heart, truncated posteriorly ; it is raised, dilated, and 

 rounded on the sides, near the anterior angles. The ocular 

 pedicles are shorter than those of the preceding subgenera, 

 and do not altogether reach the lateral extremities of the testa. 

 The intermediate anlennse are always terminated by two very 

 distinct divisions. 



In some, such as 



UCA, Latr., 



The size of the feet, beginning inclusively at those of the 

 second pair, diminishes progressively ; they are very hairy, 

 with the tarsi simply furrowed, wdthout denticulations, or re- 

 markable spines. {Cancer uca, Lin.) 



In the others, the third and fourth pair of feet are longer 

 than the second and fifth ; the tarsi have denticulated or very 

 spiny ridges. These Crustacea form two subgenera. 



Cardisoma, Latr., 



Having the four antenna;, and all the articulations of the ex- 

 ternal jaw-feet exposed ; the first three articulations of the 

 same jaw-feet are straight, the third shorter than the preced- 

 ing, emarginated superiorly, almost in the form of a heart. 

 Finally, the first of the lateral antennae is almost similar to 

 the rest, and broad. 



