114 OPHrCROlDEA. 



few papilliform spines on the most proximal upper arm-plate. 

 Three arm-spines, the uppermost the longest ; the ventral plates are 

 small, with a convex distal or, generally, a straight proximal edge. 

 Arms seven to ten times diameter of disk. 



r = 5. 



Colour white or more mottled with darker. 



Distribution. Xorth Atlantic (east side) ; Arctic Sea ; ? off Marion 

 Island. 50-2435 fms. 



a-n. 59° 26' N., 8° 23' W., 705 fms. 'Porcupine ' Exp. (St. 88). 



o-s. 60° 34' N., 4° 40' W., 560 fms. 'Porcupine ' Exp. (St. 77). 



t. 47° 38' K, 12° 8' W., 2435 fms. ' Porcupine ' Exp. (St. 37). 



u, v. 47° 38' N., 12° 8' W., 400 fms. G C. Bourne, Esq. 



Incertce sedis. 



3. OPHIOCHITON, 



Ophiochiton, Lyman, Bull. M. C. Z. v. (1878) p. 132; id. Chall. Rep. 

 Oph. (1882) p. 176. 



Disk with fine imbricated scales. Radial shields small. Mouth- 

 papillae numerous ; no tooth-papillae ; teeth present. 



1. Ophiochiton ternispinis. 



Opbiochiton ternispiuus, Lyman, Bull. M. C. Z. x. (1883) p. 255. 

 Opliioc'.iiton tenuispinus *, id. t. c. pp. 228 & 285 ; Hoyle, Proc. Roy. 



Soc. Ed. xii. (1884) p. 709, £ Proc. Roy. Phys. Soc. Ed. viii. 



(1885) p. 144. 



" Special Marls. One tentacle-scale. Three slender, rather long 

 arm-spines. 



"Description of an Individual. Diameter of disc 12 mm. Length 

 of arm 60 mm. Width of arm near disc 2 mm. Twelve mouth- 

 papilla? to each angle, whereof the four inner ones, on either side, 

 are short, pointed and spaced, while the two outer ones are flattened 

 and crowded. Teeth stout, flat, and shaped like a blunt spear-head. 

 Mouth-shields regular pointed heart-shaped, with a small rounded 

 lobe without. Length to breadth, 2 : 1*3. Side mouth-shields very 

 narrow within, where they barely meet ; but spreading widely with- 

 out, where they bound a part of the inner end of the genital opening. 

 First under arm-plate rounded and small, not larger than the neigh- 

 bouring mouth-papillae. The plates beyond are much narrower 

 than the arm ; they are about as broad as long, much wider with- 

 out than within, with an outer curve, reentering curves on the 

 sides, and a truncated angle within. They are somewhat swollen, 

 but have no ridge. Side arm-plates even, slightly flaring, nearly 



* As will be seen, the original namer of the species has, I suspect by a 

 printer's error, given two i'orins to his specific name. 





