108 BUU^ETIN "e, UNITED STATES NATIONAL MUSEUM. 



Adnmbulacral armature consisting of a saber-shaped furrow spine, and on 

 aefinal surface three to five slender slightly tapering, bluntly pointed spines, accom- 

 panied by a variable number of much smaller spinelets. Of these the innermost 

 spine stantls in line with furrow spine and is longer than latter. At base of ray the 

 remninmg four or five usually form two transverse series, bemg accompanied by a 

 number of delicate spinelets on the edge of the plate, or farther along ray one, and 

 finally both of the outer series disappear, and either one of the first series, even, 

 becomes reduced in size. The actinal adambulacral spines decrease in length 

 toward outer end of plate. They are frequently more or less flattened. One or two 

 of the spinules on outer end of plate is usually larger than the rest. 



Actinal intermediate plates each bear a tuft of spinelets, four or five in the center 

 being considerably longer than the remainder, and resembling the more slender of 

 the actinal inferomarginal spinelets. Some specimens have the actinal intermediate 

 spinelets shorter and clavatc, and only one or two in the center shghtly enlarged, 

 tlie tuft then ajjpearing much more compact. 



Mouth plates narrow but prominent. At the inner end of each plate is a diverg- 

 ing group of about twenty small papilliform spinelets on the edge between the 

 actinostoniial and furrow surfaces of jjiate. These spinelets form a several ranked 

 series or triangular group between exposed surface of plate and peristome. On the 

 exposed surface are two series of numerous spines extending to outer end of plate 

 and thence decreasing in size; sometimes only one zigzag series; spines adjacent to 

 margin much larger. Margin (adjacent to first adambulacral) has many very small 

 spinelets, partly covering the deep fasciolar groove between the plates. The first 

 adambulacral has a small group of spinelets, similar to those on inner face of mouth 

 plates, between the furrow spine and first actmal. The next three plates usually 

 have one to three spinelets in this situation. The small spinelets along the trans- 

 verse margins of first seven or eight plates are more numerous than on succeeding 

 ones. 



Madreporic body entirely hidden by paxillie. It is situated iia an intcrbrachial 

 angle, the outer margin being the width of two rows of paxillte from inferomarginals. 

 Body convex and small. 



Color in life a curious neutral olive drab or pinkish gray, yellowish white on 

 sides and actinal surface. Often some of the paxillte are whitish, causing a mottled 

 appearance. The color changes very little in alcohol. 



Anatomical notes. — Superambulacral plates present, well developed, absent from 

 first ambulacral ossicle. Unpaired oral plate or "odontophore" prominent, with 

 a well-developed keel, to which is attached lower end of the free edge of interradial 

 septum. Interradially tlie lower ends of ambulacral ossicles of two adjacent rays 

 are connected by a strong muscle band, the ends themselves being separated. This 

 allows considerable movement of mouth plates. No anus. Intestine and intestinal 

 coecum absent. Hepatic cceca extend two-thirds length of ray. Stomach occupies 

 most of disk, not divided into dorsal and ventral parts. Gonads large, extending 

 in numerous tufts depentling from abactinal body wall, in linear series nearly to tip 

 of ray. The individual bundles of tubules are rather small in specimens examined, 

 consistmg of four tubules twice dichotomously divided, making sixteen terminal 



