134 Bulletin Vanderbilt Marine Museum, Vol. VII 



face. The central mouth shield is widely cordate with the apex 

 directed outward, rounded. The side mouth shields are small, 

 triangulate, well separated at their inner angles, where each sup- 

 ports a strong, conical tooth. The vertical oval contains numerous 

 small denticles, closely crowded. 



The five arms are very long, about ten times or more the disk 

 diameter, slender and very flexible. The dorsal arm plate is 

 trapezoidal, being narrow and nearly straight on the proximal 

 margin with the lateral margins obliquely divergent and the 

 lateral angles rounded, the distal margin widely rounded, forming 

 a continuous convexity; the length of the plate being nearly a 

 third greater than its width. 



The side arm plates are wide and support on the proximal 

 joints ten arm spines which soon decrease to eight farther down 

 the arm, which form a comb-like series, the ventral six, or four 

 spines, being the longest of the series, these decreasing in length 

 from the most ventral toward the dorsal, while the dorsal four 

 spines are noticeably much shorter than those preceding and like- 

 wise decrease in length dorsad. The apices of the ventral four 

 arm spines are each produced into a claw-like procurved tooth or 

 spine distally, which is directed ventrad in almost every instance. 

 The arm spines are stout, laterally compressed and under mag- 

 nification show a continuous series of fine spinules or rugosities 

 arranged in longitudinal series on the side of the spines, with a 

 terminal cluster of coarser sharp spines which on the longer arm 

 spines not infrequently are developed as procurved hooks. The 

 narrowed lateral margins of the arm spines are also beset with 

 irregular rough spinules. 



The under arm plates are with the angles rounded, the lateral 

 margins reenteringly curved and the distal margin slightly con- 

 cave. The single tentacle pore is large. 



References: Ophiothrix expedita, Koehler, R., Siboga-Expe- 

 ditie Ophiures Littorales, Monogr. XLVb, vol. XXV, Leiden, 

 1905, p. 96, pi. 19, figs. 10-14, pi. 15, fig. 5.— Clark, H. L., 

 Mem. Mus. Comp. Zool., vol. XXV, 1915, p. 272.— Koehler, 

 R., Bull. 100, U. S. Nat. Mus., vol. V, 1922, p. 229, pi. 31, fig. 6, 

 pi. 33, fig. 5 and pi. 98, fig. 5 also listed as variety rhabdota 

 (H. L. Clark) , p. 230, pi. 31, fig. 5. 



