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. 
We 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 antennae 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, without 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 antennae, 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. 
