OPHIOCTEN. 113 



seen entire ; arm-spines three, the upper one rather long and stout, 

 tapered, the others successively shorter and smaller ; two tentacle- 

 scales. Lower arm-plates rather small, transversely rhomboidal, 

 with rounded lateral angles, the four sides concave, and the distal 

 angle prominent : near the base of the arms the plates are in con- 

 tact to a small extent, but farther out they are separated by the 

 lateral plates. Upper arm-plates large, thickened, trapezoidal, 

 toward the base of the arms broader than long, broadest distally, 

 the proximal and distal edges nearly straight ; farther out they 

 become longer than broad, and much narrowed proximally. 



_ " Colour, in life, bright orange ; in alcohol, white. Diameter of 

 disk 18 mm. ; its height 7 mm. ; length of arms (minus tips) from 

 centre of disk 45 mm. 



" Off Martha's Vineyard, 192 to 310 fms. 



" Specimens of this singular species were sent to Mr. Lyman for 

 examination last year. He considered it an undescribed species. 

 It has no allies on our coast/' 



2. OPHIOCTEN. 



Ophiocten, Liitk. Vid. Medd. 1854 (1855), p. 97 ; id. Dansk. Selsk. 

 Shift, v. (1859) p. 51 ; Lyman, 111. Cat. M. C. Z. (1865) p. 53 ; id. 

 Cball. Rep. Oph. (1882) p. 78. 



No tooth-papilla? ; teeth ; mouth-papillse not numerous. Disk 

 not notched ; radial shields partly obscured by characteristic scaling 

 of disk. Arm-spines solid, smooth, short, not stout. Bursal slits 

 not very extensive. 



Allied to Ophiura, but more delicate. 



1. Ophiocten sericeum. (Plate XIII. figs. 1 & 2.) 



Ophiura sericea, Forbes, Sutherl. Voy. (1852) ii. p. ccxv. 



Ophiocten kroyeri, Liitk. Vid. Medd. 1854 (1855), p. 102 ; id. Dansk. 



Selsk. Skrift. v. (1859) p. 52, pi. i. fig. 5 ; Lym. III. Cat. M. C. Z. 



(1865) p. 53 ; Ljunc/man, (Efv. Vet.-Akad. Fork. 1864 (1865), p. 360; 



id. op. cit. 1866 (1867), p. 307 ; Marenz. Denk. Ak. Wien, xxxv. 



(1878) p. 382. 

 Ophiocten sericeum, Lym. Bull. M. C. Z. v. (1879) p. 102 ; Dime. $ 



Slad. Greenl. Ech. (1881) p. 65, pi. iv. furs. 8-10 & 14 ; Lym. Chall. 



Rep. Oph. (1882) p. 79; Hoxjle, Proc. Roy. Soc. Ed. xii. (1885) 



A small and delicate species. 



The disk flattened, with a sharp edge, and covered for the most 

 part with a scaling which renders indistinct the underlying plates, 

 but a central circular plate with larger primary plates around 

 it may be made out. Three to five distinct, proportionately well- 

 developed mouth-papillse ; rather large, irregularly oval, mouth- 

 shields ; elongated side mouth-plates. Arms flat, rather long ; a 

 comb on either side of the base of about seven short spines, and a 



