72 GAMMARID^E. 



AMPHIPODA L YSIANASSIDES. 



NATATOItlA. 



a. First pair of gnathopoda strong ; second pair feeble and 

 imperfectly cheliform. 



Genus LYSIANASSA. 



Lysiatiassa, EDWARDS, Ann. des Sc. Nat. t. xx. Hist, des Crust, t. iii. 

 p. 20. DANA, U. S. Explor. Exped. p. 908. 



Generic character. Superior antennae very short, stouter than 

 the inferior, appendiculate. First pair of gnathopoda not sub- 

 cheliform. Second pair imperfectly developed, but long, mem- 

 branous, and subchelate. Telson single, squamiform, entire. 



THIS genus may be distinguished by its short upper 

 antennae being very stout near the head, and suddenly 

 reduced in size at the base of the flagellum, which is 

 very short, and carries a secondary appendage. The 

 inferior antennae are more slender and often longer than 

 the superior. The mandibles are furnished with a 

 jointed appendage, and armed with a sharp, smooth, 

 cutting edge, carrying a stout tubercle upon the anterior 

 margin. The pair of foot-jaws have large squamous pro- 

 cesses attached to the third and fourth joints. The first 

 pair of limbs are not formed into a claw, but terminate 

 in a straight finger, which imperfectly bends upon the 

 hand. The second pair are feeble and very long : this 

 latter circumstance is due to the great length of the 

 third joint, which, in most of the animals of this Order, 

 is very short. The coxae of the four anterior pairs of 

 limbs are deeper than the segments of the body to 



