Y 



H 



156 



THE 0PHIURID7E. 



usually seen some irregular scales^ a little larger than the others (not seen in 

 the figure). The radial shields are not half as long as the radius of the disk, 

 in contact in their outer half, their inner ends separated by more irregularly 

 arranged scales ; they are pointed within^ truncated without. Usually no 

 scales are seen outside the radial shields. Under side of the disk covered 

 with a close granulation^ only just outside the mouth shield may be seen 

 some few scales. Inner end of the genital scales distinct. The margin of 

 the disk is convex, the edge rather sharp. 



Three equal, tapering arm-spines, about as long as an arm-joint. Two 

 rounded tentacle scales, that on the ventral plate the larger. 



Color in alcohol : white, the disk with a pale bluish tint (from the 



stomach). 



One specimen from Station 3355, 182 f., 5 specimens numbered 8158.* 



The radial shields in some specimens are rounded, almost wholly in con- 

 tact, only their inner ends being separated by one small scale (Fig. 3). The 

 primary plates may be distinct. 



This species evidently belongs to what is commonly called OjMocnida. 

 However, we have named it Ainj}hiura^ as we think Ojjhiocnida to be an un- 

 natural genus, spines or granules on the disk being too insufficient a charac- 

 ter for founding a genus upon. The genus AvijAijAolis Ljungm. is much 

 better defined, and Lyman was scarcely right in including those forms in the 

 genus AmpJdiira. Our A, gramd(da would be an Amphiplwlis. 



Also the next two species, A. gastracanlha and A, notacantlia^ would be- 



long to Opliiocnida on account of the spines on the disk. Lyman 



says 



(Challenger, p. 152), " OjMocnida is AmpUura beset with small spines or 

 grains, just as OpUadis is Amphiura with short wide arms." He is only 

 partly right in that; OpUocnida is really AmijJdura, it is true, but OpM- 

 actis is very well separated from AmpUura by having a single (or no) infra- 

 dental papilla; whereas Amphiura always has two. 



36. Amphiura gastracantha n. sp 



Plate XIII. Figs. 4-6. 



Diameter of disk, 8 mm. ; width of arm close to disk, without spines, 

 1 mm. ; length of arms, not known with certainty, but they are long and 



* Wc have no information of what this number means. 



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