166 CLASS CRUSTACEA. 



tions, sometimes, as in his Pisa properly so called, the length 

 of the feet diminishes gradually ; sometimes the third feet 

 are abraptly shorter than the preceding in the males. This 

 takes place in his Chorinus. Of these four genera of Dr. 

 Leach, the prototype species are, Pisa aurita, Latr. ; Pisa 

 cliiragra, ejusd. ; Pisa XypMas, ejusd. ; and Pisa heros, 

 ejusd. 



Pericera, Latr., 



Approximating to pisa in the form and proportions of the 

 claws and the number of the segments of the tail, are remote 

 from them as well as from the anterior subgenera, inasmuch 

 as the lateral antenna3 are inserted under the muzzle, and 

 more sensibly approaching the fossets which lodge the inter- 

 mediate ones, than those which receive the ocular pedicles. 

 {Maia tauriis, Lam.) 



In the two following subgenera the ocular pedicles are 

 short or middle-sized, as well as in the preceding. But the 

 claws, even those of the males, are scarcely thicker than the 

 following feet. The tail is always composed of seven seg- 

 ments. 



Maia, Leach. 



In these the second articulation of the lateral antennae ap- 

 pears to spring from the internal canthus of the ocular cavi- 

 ties. The hand, and the articulation which precedes it, are 

 almost of the same length. The testa is ovoid. {Inaclius 

 Cornutus, Fab., the Cancer squinado, of Herbst.) 



MiCTPPUS, Leach, 

 Have the first articulation of the lateral antennae bent, dilated 



