150 
CLASS CRUSTACEA. 
spine. The tail of the males is often very different from that 
of their females. These portuni compose the genus Lwpa of 
Dr. Leach, and are, for the most part, tolerably large, and 
exotic. The Mediterranean presents us with one species — 
Portunus Dufourii , Lat. 
A third division shall be composed of species analogous to 
the last in the form of the testa, but whose lateral teeth, com- 
monly five in number, are almost equal, or the posterior one 
of which differs but little from the preceding. The length of 
the claws but little exceeds that of the testa. 
Those which have from six to nine teeth on each side are 
all exotic. (P. Tranquebarius , Fab. Herbst.) is the only 
known species, having nine teeth, and all equal at each late- 
ral edge. 
The following species, all of the European seas, have five 
teeth at each lateral edge of the carapace. Cancer puber , 
L. — C. corrugatus , Penn. Zool. Brit. — C. mamas, Lin. Fab. 
( Common crab of our coasts.) This appears to us to belong 
to Portunus, rather than to crab properly so called. 
We shall form a fourth division with the subgenus 
> Platyonichus, 
Whose denomination has replaced that of portumnus of 
Dr. Leach, too much approximating to the word portunus , 
already employed. Here the testa is at least as long as broad, 
and almost in the form of a heart. All the tarsi of the feet, 
the claws excepted, are terminated by a small semi-elliptical 
lamina, elongated and pointed ; the index is very much com- 
pressed. This division again comprehends but a single 
species, which is the cancer latipes of Plancus. The front 
presents three teeth, and each lateral edge of the testa five. 
From the swimming crabs we pass to those, all of whose 
feet terminate in a point, or by a conical tarsus, sometimes 
