150 CLASS CRUSTACEA. 



spine. The tail of the males is often very different from that 

 of their females. These portmii compose the genus Lupa 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. Tranqueharius, 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 piiher, 

 L. — C corrugatus, Penn. Zool. Brit. — C. iiKBnas, 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 fi'ont - 

 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 



