246 RECENT OPHIURANS. 



fine scales, more than 12 series from center to margin and 9-11 across an inter- 

 radial area; primary plates not distinguishable. Radial shields small, wide 

 and rounded (hence the name), 1.3 mm. long, .7 mm. wide, closely in contact. 

 Upper arm-plates twice as wide as long, or even wider; proximal margin much 

 narrower than distal which is more or less convex; lateral margins rounded. 

 Interbrachial areas below covered with very fine scales, the most distal series 

 of which stands almost vertical and shows above the coarser scaling of the disk 

 as a very delicate border. Oral shields (except madreporite) diamond-shaped, 

 much longer than wide; madreporite ovate, somewhat larger than the other 

 shields. Adoral plates, rounded trigonal, meeting within. Oral papillae, 3 on 

 each side, the distal one usually largest; subdental papillae small, narrow, 

 divergent orally; distal papillae, large, thick, angular, as long as wide; middle 

 papillae, thick and concave proximally where they overlap the subdental ones; 

 in specunens other than the type, they may be as large as the distal ones and 

 are sometimes larger. Under arm-plates distinctly wider than long, pentag- 

 onal with a proximal angle and distal margin more or less notched; separated 

 or somewhat in contact. Side arm-plates moderate, often meeting below but 

 not above; each plate carries 3 arm-spines, subequal, terete, acute, and rather 

 longer than an arm-joint. Tentacle-scales 2, large and subequal. Color (dried 

 from alcohol), disk grayish, arms pale brownish or fawn-color. 



Five PARATYPES (M. C. Z. 1442), four lacking the disk. Porto Rico: Maya- 

 GTJEZ Harbor, 4| fms. Fish Hawk Station 6057. 



This species is the one recorded in my report on the echinoderms of Porto 

 Rico (1901. Bull. U. S. Fish Comm., 2, p. 247) as Amphipholis goesii Ljungman. 

 It is not that species and is better regarded as an Amphiodia than an Amphi- 

 pholis, though in some specimens the distal mouth papilla is much the largest. 

 Specimens 9 mm. across the disk have more numerous disk-scales than the 

 type, there being more than 20 series between center and interradial margin and 

 16-18 across an interradial area. Comparison of our specimens with other 

 West Indian species of Amphiodia show that atra is probably the nearest relative 

 of gyraspis, the disk-scaling and the arm-spines and plates being quite similar 

 in the two. In atra however the radial shields are very much larger and the 

 scaUng of the interbrachial areas, below, is noticeably finer. Other minor differ- 

 ences are also present, but as there is only one imperfect specimen of atra at hand 

 for comparison, these may prove to be individual peculiarities. The holotype 

 of this species is in the U. S. N. M., Cat. No. 34587, and is from the same Fish 

 Hawk station as the paratypes listed above. 



