166 
CLASS CRUSTACEA. 
lions, sometimes, as in his Pisa properly so called, the length 
of the feet diminishes gradually ; sometimes the third feet 
are abruptly 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 aiirila , Latr. ; Pisa 
chiragra , ejusd.; Pisa Xyphias , ejusd. ; and Pisa keros , 
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 antennae are inserted under the muzzle, and 
more sensibly approaching the fossets which lodge the inter- 
mediate ones, than those which receive the ocular pedicles. 
{Mata tauras , 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. 
Mai A, 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.) 
Mi cirrus, Leach , 
Have the first articulation of the lateral antennae bent, dilated 
