284 bulletin: museum of comparative zoology. 



rounded angles and concave sides; they are separated radially by the 

 first under arm-plate and interradially by a large depression or pore, 

 which occupies the surface of the jaw, much as in Ophiothrix. The 

 oral plates are small but distinct and well-developed. There are two 

 oral papillae on each side, as in Amphiura, a big block-like one proxi- 

 mally and a very small flat, bluntly pointed one distall}' where the 

 oral and adoral plates meet. 



Amphipholis pachybactra, sp. nov, 



iraxv^ = thick -f fioLKTpov = club, in reference to the very thick middle 



arm -spine. 



Plate 1, fig. 3-5. 



Holohjpe.— M. C. Z. 4,140, and 6 Paratijpes, M. C. Z. 4,141. 

 British West Indies: Tobago, Buccoo Bay, Sandy Point, April, 

 1916, in sandy mud in 2-3 ft. of water, in company with Ophionema, 

 Ophiophragmus, Ophiocnida, and other amphiurids. Carnegie Ex- 

 pedition. H. L. Clark coll. 



Disk, 6 mm. in diameter; arms 65 mm. long. Disk slightly puffed, 

 especially in theinterradial areas, covered with a coat of rather thick 

 but very small scales, about a dozen series in each interradial area 

 where narrowest; no primary plates distinguishable. Radial shields 

 small and closely joined, except at inner end; they are not one milli- 

 meter long, and the width of each is evidently less than half its length. 

 Upper arm-plates fully twice as wide as long, barely in contact; basally 

 they are very broadly triangular with a proximal angle and truncate, 

 rounded lateral angles but they become more and more ellipsoidal 

 by the rounding of the angles. Interbrachial areas below covered by 

 a coat of fine scales, noticeably smaller than those on the upper sur- 

 face of disk. Oral shields, spearhead-shaped, widest distal to middle, 

 proximal angle acute, distal angle rounded, almost as wide as long. 

 Adoral plates moderately large, wider without than within where 

 they meet fully ; radially they are separated by first under arm-plate. 

 Oral plates small and difficult to make out. Oral papillae, 3 on a 

 side, of which the distal is .25-.30 mm. wide, as wide as the other two 

 together; the latter are subequal and lie side by side, the proximal 

 not standing close to its fellow on the tip of the jaw. Under arm- 

 plates pentagonal; with a sharp proximal angle, and the distal, lateral 



