Boone, Echinodermata, Cruises of "Ara" and "Alva" 145 



with rounded angles. There are ten to twelve teeth, small, blunt- 

 ish, arranged in an oval. 



There are six arms ; these are short, proximally thick, distally 

 tapered to a blunt tip, TTie dorsal surface of the arm is encased 

 in tough integument like that of the disk, which entirely conceals 

 the dorsal, side, and ventral arm plates. There are apparently 

 two transverse rows of coarse, bead-like tubercles to each articu- 

 lation of the arm, one series of tubercles being between and in 

 line with the bases of the arm spines, and the second series of 

 tubercles is about halfway between these and the first series of 

 tubercles of the next joint. 



Each side arm plate supports five spines, which are proximally 

 encased in tough skin, appearing to arise from a common, pro- 

 jected, thick base, not unlike the palm of a hand, from which five 

 short spines radiate. Of these, the dorsal spine is very short, as 

 is also the ventral, fifth, spine. The second, or next to dorsal, spine 

 is twice as long as the first spine ; the third and fourth spines are 

 subequal, each being slightly longer than the second. All five 

 spines are conical with the sides filled with short, sharp spinules, 

 which toward the apex become coarser, more acuminate and more 

 numerous. 



The ventral arm plates are of medium size, skin-encased and 

 appear to be squarish, with the distal margin lightly rounded, the 

 lateral margins slightly concave. 



The tentacle scale is situated in advance of and nearly opposite 

 the fifth or most ventral arm spine. 



References: Ophiothela dayiae, Verrill, A. E., Proc. Boston 

 Soc. Nat. Hist., 1869, vol. XII, p. 391.— Lyman, Th., Mem. 

 Mus. Comp. Zool., vol. IV, 1875, D. 4, fig, 60. — Lyman, 

 Th., Kept. Sci. Res. H. M. S. "Challenger" Zool,, 1882, 

 vol. V, pt. Ophiuroidea, p. 230. — Marktanner-Turneret- 

 SCHER, G., Ann. K. K. Naturh, Hofmus. Wien, 1887, Bd. II, 

 p. 313, — Doderlein, L,, Denksch. Med,-Naturw, Gesell, 

 Jena, 1896, Bd. VII. text p. 297, p. 486, atlas, pi. 17, 

 figs. 25-ab; in Semon, Zool. Forschungsr. in Australien und 

 Malayischen Archipel, pt. V, text, p. pt. V, atlas. — Koehler, 

 R., Bull. Sci. France-Belg., t. XXXI, 1898, p. 89; Siboga- 

 Expeditie, Ophiures Littorales, Monogr. XLV-B, 1905, p. 117 ; 

 Bull. Mus. Hist. Nat. Paris, t. 1905, t. XI, 458; Bull. 



