DECAPOD!. 181 



of the shell smooth. The tale of the males presents, at most, but 

 MX eomplrtr segments*. 



PISA, Leach. 



Claws of amean size, with pointed fingers ; tibia; without any spine 



beneath, and the tail composed of seven segments in both sexes. 



As in the preceding subgenera, the lateral antennae are inserted at 



an equal distance from th that n-c' iv< thr intermediate 



. and from the ocular cavities, or rather nearer to the latter. 



Tin M-, as in the u da ,Leach f, have two ranges of den- 



tations on the under part of tin- tarsi. Those have but a single row 

 of dentations, or a simple fringe of thick claviform cilia, under the 

 same joint. The latter constitute the genus Lissa of that author J. 



Among those which have a range of dentations, the feet some- 

 tim.'s gradually diminish in length, as happens in his Pisa, pro- 

 perly M> called, and at others, the third ones, in the males, become 

 abruptly shorter than those which precede them, as in his C/tori- 

 nus\\. 



PERICERA, Lair. 



The Pericerae, though approaching the Pisae in the form and pro- 

 portions of the claws, and the number of their caudal segments, are 

 removed from them, as well as from the other anterior subgenera, 

 hy the insertion of their lateral antenn* under the snout, and their 

 approximation to the fossuloe lodging the intermediate ones, being 

 closer than to those which receive the ocular pedicles If. 



In the two following subgenera the ocular pedicles are short or 

 moderate, as well as in the preceding ones. But the claws, even 

 tho>- of the males, are hardly thicker than the following feet. The 

 tail always consists of seven segments. In the 



MAIA, Leach, 



The second joint of the lateral antennae seems to arise from the 

 internal e.mtlius of the ocular fossae. The hand and the joint which 

 precedes it are nearly of the same length. The shell is ovoid. 



Tli is subgenus established by Lamarck, and originally consisting 

 of a great number of species, comprises, at present, according to 

 the method of Dr. Leach, but one, the Cancer squinado, Herbst, XIV, 



Mow ylabra, Collect. <lu Mas. d'Hist. Nat.; Alaia lunulata, Risso, I, 4; 

 Libiniu lunulata, Desmar. 

 t Pitaourita, Latr., Encyc. Method. P. monoceriu, Ib. 



Latr., Encyc. Method.; Desman, Consul. 



$ Pita xypkiat, Latr., II). : I-JUM!., Ib. P. aries\P. barbicornis ; P. corni* 

 P. ttyXiP.bicontuta.P, triipinosa .- P. amutta. Leach, Malac. Brit., 



Cancer musconu / Lin.; P. tctraodon, Lcacb, Ib. xx. 

 || Pisa heros, Litr.. Kn.-yc. Method. 

 j Main ttwnu, Lam. ; Cancer cv> \ !>st., lis, 6. 



N.H. The genus Amathia of M. P. Roux, Hist, dcs Crust, de l;i Mo<lite>rr., &c. f 

 I , does not differ from my Peru-era it even appears to me to have the same 

 type. The Lithojrrapbic plates which accompany this work are distinctly and 

 faithfully executed. 



