NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 109 



lar to that so characteristic of Amphiodia digitula. First under ami 

 plate minute, squarish; succeeding plates somewhat hexagonal or 

 pentagonal, about as wide as long, more or less in contact on basal 

 part of arm; on many of them there is a minute tooth or sharp pro- 

 jection at the center of the distal margin. Side arm plates small, each 

 with only three sharp, subequal spines, about as long as the joint or a 

 little longer. Tentacle scales, two. Color (dried from alcohol), nearly 

 white, or light grayish-brown; upper and under arm plates some- 

 times rather heavily shaded with dull brownish-red. 



Localities. Albatross station 3695, off Tsuragi Saki Light, Honshu 

 Island, Japan, 110 to 259 fathoms, green mud, fine sand, 30 speci- 



FIG. 75. AMPHIOPLUS ACANTHINUS. < 4. a, FROM ABOVE; 6, FROM BELOW; c, SIDE VIEW OF THREE 



ARM JOINTS NEAR DISK; d, REGENERATED DISK AND THREE REGENERATED ARMS. 



mens; station 5073, Suruga Gulf, lat. 34 46' N.; long. 138 21' 50" 

 E., 148 fathoms, gray mud, bottom temperature 54.6, 2 specimens. 



Type. Cat. No. 25595, U.S.N.M., from station 3695. 



This is an unusually well-characterized species and yet its generic 

 position is somewhat in doubt. As an Ampliioplus it ought not to 

 have spines on the disk, while, on the other hand, it will not go into 

 Verrill's genus Amphilimna, where spiny-disked species of AmpTiio- 

 plus ought to go, for it does not have "six to ten" arm spines, nor are 



the tentacle scales "spiniform," nor are the radial shields ''parallel, 



