AORA. 279 



AMPEIPODA. GAMMARIDES. 



NATATOBIA. 



Genus— AORA. 



Aora. Kroyer, Tidsk. ser. 2, i. p. 335, 1845. Spence Bate, Cat. 



Amph. Brit. Mus. p. 160. 

 Lalaria. Nicolet, in Gay's Historia de Cliile, vol. iii. 1849. Spence 



Bate, Ann. Nat. Hist. xx. p. 525, 1858. 

 Loncliomerus. Spence Bate, Rep. Brit. Assoc. 1855, p. 58. Ann. Nat. 



Hist. 2 ser. xbc. p. 143. White, Hist. Brit. Crust, p. 180. 



Generic character. Superior antennse longer than the in- 

 ferior; furnished with a secondary appendage. First pair of 

 gnathopoda larger than the second, having the ineros infero- 

 distally produced as far as the e.xtremity of the carpus. Seventh 

 pair of legs longest. 



In this genus the animal is long and slender. The 

 superior antennae are very long and are furnished with a 

 slender secondary appendage. The inferior antennas are 

 about half the length of the superior and furnished with 

 a very short flagellum. The first pair of legs are very 

 long, complexly* chelate, having the metacarpal joint 

 infero-distally produced so as to meet the apex of the 

 finger when closed. The second pair of legs are sub- 

 chelate and much smaller and shorter than the first. 

 The last pair of walking legs are much longer than the 

 others. The caudal appendages are double-branched, 

 and the terminal caudal plate is tubular. 



The modifications of form, and consequently of func- 

 tion, which the two first pairs of legs undergo in different 

 groups of Amphipoda are nowhere more interestingly 



* We use the term ' ' complexly chelate " where the prehensile organ is 

 formed by more joints than the jiropodos and dactylos. 



