NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 161 



broadly in contact, with distal margin somewhat concave. Side arm 

 plates small, not meeting either above or below; each plate carries 

 three terete, sharp arm spines, of which the middle one is a trifle the 

 longest and may exceed the joint. Tentacle scales two, rather large. 

 Color (dried from alcohol), pale fawn-color, or yellowish-brown. 



Localities. Albatross station 2885, off Oregon, lat. 45 56' N. ; long. 

 124 2' W., 30 fathoms, fine gray sand, bottom temperature 49, 1 

 specimen; Captains Harbor, Unalaska, 9 to 15 fathoms, stones and 

 mud, Dall collection, 1 specimen. 



Type.C&t. No. 16391, U.S.N.M., from Captains Harbor, Un- 

 alaska. 



The type-specimen is labeled " Amphiura occidentalis," and there is 

 no doubt that periercta is closely related to that species. But a 

 glance at the arm spines is sufficient to distinguish the two, for in 

 occidentalis they are thick, flattened, and remarkably blunt, while 

 in periercta they are terete and sharp. 



FIG. 69. AMPHIODIA ANCISTROTA. x 5. a, FROM ABOVE; 6, FROM BELOW; c, SIDE VIEW OF THREE ARM 



JOINTS NEAR DISK; d, NEXT TO THE LOWEST ARM SPINE, X 10. 



AMPHIODIA ANCISTROTA, new species." 



Disk 10 mm. in diameter; arms about 50 mm. long. Disk covered 

 by numerous small scales, which are somewhat smaller at the inter- 

 radial margins than elsewhere; disk tends to be pentagonal with 

 sides indented. Radial shields small, divergent, touching distally. 

 Upper ends of genital scales, usually visible, just distal to radial 

 shields, each often with a small, projecting spinelet. Upper arm 

 plates, somewhat tetragonal, twice as wide as long, narrower prox- 

 imally than distally, broadly in contact; lateral and proximal margins 

 tend to merge into a continuous curve. Interbrachial spaces below 

 covered with a coat of very fine scales. Oral shields, broadly oval, 

 wider than long. Adoral plates nearly horizontal, very narrow at 

 inner end, so broad at outer end that they look almost triangular. 

 Oral papillae, three on each side, subequal, rounded, and a fourth 

 smaller at outer corner of mouth angle; the one at apex of jaw is the 



, signifying hooked, in reference to the hooked arm spine. 

 34916 Bull. 7511 - 11 



