1909. 



CRUSTACEA OF THE GENUS GENNADAS. 



721 



of the petasma are so complicated that they almost defy adequate 

 textual treatment ; the necessary information is consequently 

 conveyed solely by the figures. 



All that is at present known of the habits of Gennadas and 

 Amalopenceus goes to prove that they are free-swimming forms 

 which never live on the ocean bottom. It is probable that all the 

 specimens found by the ' Challenger ' were caught during the 

 a,scent of the net ; the depths given can therefore be accepted only 

 as indications of the soundings at the different stations. 



Gennadas parvus Spence Bate. (Plate LXXIII. figs. 1-6 ; 

 Plate LXXY. fig. 1.) 



Gennadas jxirvics, Sp. Bate, Ann. Mag. Nat. Hist. Sept. 1881, 

 p. 192, and ' Challenger ' Crustacea Macrura, 1888, p. 340, 

 pi. lix. 



'^ Gennadas 2^arvi(,s, Wood-Msison, Ann. Mag. Nat. Hist. Feb. 

 1891, p. 189, and Oct. 1891, p. 286. 



? Gennadas parvus, Alcock, Desc. Cat. Indian Deep Sea Macrura, 

 1901, p. 46. 



'^Gennadas j'xtrmts, Rathbun, U.S. Fish Comm. Bull, for 1903 

 (pubL 1906), p. 907, fig. 60. 



St. 230. S. of Japan. 26° 29' N., 137° 57' E. Trawl. 2425 

 fathoms. One male, the type specimen, 25 mm.* 



The rostral crest (PI. LXXIII. fig. 1) is elevated above the 

 dorsal cai-ina of the carapace ; its frontal margin is rather strongly 

 convex. It bears the usual fringe of setae between the apex and 

 the dorsal spine, while behind the latter there is a small tubercle 

 situated on the dorsal carina of the carapace. Both the antennary 



* Measured from the apex of the rostrum to the tip of the telson. 



Proc. Zool. Soc— 1909, No. XLIX, 49 



