fart 1 garth: pacific oxyrhyncha 181 



At the time, and for more than a decade subsequently, Rathbun's 

 determination of the Galapagos Islands specimens prevailed. Upon 

 mature consideration, and supported by many more specimens of Tyche 

 lamellifrons from the American mainland than the single Gulf of Cali- 

 fornia male (U.S.N.M. No. 21905) available to Miss Rathbun, in- 

 cluding specimens from Bell's type locality, the Bay of Panama, the 

 writer is inclined to his former view. Certainly, Rathbun did not con- 

 sider the totally dissimilar third maxillipeds, that of the new species 

 transcending the limitations of the genus Tyche as given by her (1925, 

 p. 507). Additional evidence for separating the Galapagos Islands speci- 

 mens from those of the mainland and of Clarion Island is furnished by 

 the male first pleopod, the triangular opening of which is unprotected by 

 the flap which in T. lamellifrons covers it to the very tip. 



It is the maxilliped and pleopod upon which the new species should 

 rest, rather than relative length of rostral to preorbital horns, which is 

 subject to considerable variation, even in the short series of six specimens. 

 The one sizeable male is asymmetrical with respect to the rostrum, the 

 right horn being longer than the left and extending beyond the pre- 

 orbital. For this reason it was not selected as the type, although this 

 would have been desirable from the standpoint of the pleopod. 



The type specimen was figured as Tyche lamellifrons (Garth, 1946, 

 pi. 54, figs. 1, 2, 5, 6), figures 3 and 4 of the same plate being of the 

 male paratype from station 343-35. 



Subfamily ACANTHONYCHINAE 



Acanthonychinae Alcock, 1895, pp. 160, 164, 190. Rathbun, 1925, p. 



140. Stephensen, 1945, pp. 99, 218. 

 Acanthonychidae, Stebbing, 1910, p. 286. 



Eyes without true orbits ; the eyestalks very short or sometimes even 

 obsolescent, either concealed beneath a forwardly-produced supraocular 

 spine, or sunk in the sides of a huge beaklike rostrum ; a postocular spine 

 or process sometimes present, but not excavated for the reception of the 

 retracted eye. Basal antennal article truncate-triangular. External maxil- 

 lipeds with the merus as broad as the ischium. Dactyli of the ambulatory 

 legs prehensile or sub-chelate; the last three pairs of legs often dis- 

 proportionately short compared with the [first] pair. (Alcock) 



Rathbun (1925) points out that the postocular spine is not cupped 

 (except in Sphenocarcinus) , that the rostrum may be either simple or 

 two-spined, and that the palp arises from the anterointernal angle of the 

 merus of the maxilliped. 



