EEPORT ON THE OPHIUROIDEA. 79 



OpUocten sericeum (?), Ljn. (PI. XXXVIII. figs. 18-21). 



Ophioden sericetim, Ljn., Tillag Skan. OpL Of. Kong. AkaJ., p. 360, 1864; Lym., Bull. Mus. 



Comp. Zool, vol. V. p. 7, pi. 102. 

 Ophioden Krnijeri, Ltk., Vid. Meddel, p. 8, 1854; Addit. ad Hist., part 1, p. 52, pi. i. 



figs. 5''-5'' ; Lym , lU. Cat. Mus. Comp. Zool., No. i. p. 53. 

 Ophlura sericea, Fbs., SutL Journ. Voy. Baffin's Bay, vol. ii., App. 

 Ophioghjpha gracilis (?), G. 0. Sars (young), Vid. Selsk. Forh., p. 18, 1871. 



Ophiocten sericeum seems not to differ essentially from Ophioglypha gracilis, except 

 in having a comb of fine papillas along the outer edges of the basal upper arm plates ; 

 but this comb is wanting in the young, and not regular in the adult. A young Ophioc- 

 ten sericeum (disk 7 '5 mm.) was very like a stiU smaller Ophioglypha gracilis (disk 

 6 "8 mm.), which had the arm comb less marked; but other specimens had it just the 

 same. A number of specimens marked as Ophiocten sericeum (young) and Ophioglypha 

 gracilis showed variations in number of papillae fllong the genital openings, coarseness of 

 disk scales, more or less pointed tentacle scales, and length of spines ; but all these 

 variations seem common to both, in a greater or less degree. The two specimens of 

 the Challenger Expedition showed no valid difference with the half-grown Ophiocten 

 sericeum, except in absence of papillae along the genital opening ; but two specimens 

 from George's Bank, off Massachusetts, were in this respect intermediate, and had hardly 

 any papillae in that region. 



Off Marion Island : 50 to 75 fathoms. 



Ophiocten amitinum, Lym. (PI. IX. figs. 7-9). 



Ophioden amitinum, Lym., Bull. ]\Ius. Comp. Zool., vol. v. part 7, p. 100, pi. v. figs. 129, 

 130, 1878. 



Primary and marginal disk plates large and conspicuous. Arm comb and papillae on 

 first two upper arm plates well marked. Two minute tentacle scales, 



(Type specimen from Kerguelen Island.) Diameter of disk 7 mm. Length of arm 

 about 35 mm. Width of arm without spines 1'5 mm. Four short blunt mouth 

 papillas on each side, and one longer and pointed at apex of jaw. Mouth shield 

 large, pentagonal, broader within than without, having a wide angle within, and outer 

 corners curved ; length to breadth 1'3 : 1'4. Side mouth shields small, broader without 

 than within, where they meet and are often somewhat separated from the mouth shield. 

 First under arm plate large, rounded triangular, with outer edge straight ; the re- 

 maining plates small and three-sided, much wider than long, with outer edges strongly 

 curved and inner laterals re-enteringly curved, the whole presenting almost a crescent 

 shape ; they become very small towards tip of arm. Side arm plates broad, flaring 

 somewhat outward, meeting broadly below ; sej^arated above by the upper arm plates, 

 which are broader than long, with lateral sides straight, and outer edge, which is 



