14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



areole there is a row of scrobicular tubercles, interrupted below on the 

 areoles at the ambitus, and both above and below on those below the 

 ambitus. In the midline of the interambulacra below, but not above, 

 the ambitus there is a somewhat irregular row of smaller tubercles 

 between the scrobicular tubercles surrounding adjacent areoles so that 

 the midline of the interambulacra is completely filled with tubercles. 



The diameter of the apical system is one-half that of the test at the 

 ambitus. The oculars are all rather widely exsert. The genital pores 

 are small, and are situated about one-third of the distance from the 

 outer apex to the inner edge of the genital plates. The genital plates 

 are 2.8 mm. wide at the base and 2.4 mm. long in the midline. The 

 oculars bear 7-9 tubercles, the genitals 14-18; each of the small plates 

 in the periproctal area bears a single tubercle, some of the larger 

 peripheral ones sometimes having 2 or even 3. As the tubercles on the 

 genital and ocular plates are rather widely separated, the dense mass 

 of secondary spines on the periproctal plates is separated from the 

 row of closely placed spines along the outer borders of the oculars 

 and genitals by a conspicuous, almost completely naked, band about 

 1.5 mm. wide. 



The peristome is almost flat. There are 10-11 plates in each am- 

 bulacral series, and 4 in the interambulacral series. 



The primary spines are about one-third again as long as the hori- 

 zontal diameter of the test. They are fairly slender, slightly flattened, 

 and taper gradually to an abruptly truncated, though not expanded, 

 tip. The shaft is closely set with granules arranged in 13 or 14 longi- 

 tudinal lines which just at the tip of the spine become ridges. The 

 granules in each line alternate with those in the lines on either side. 

 On the oral side of the spine these granules are low, elongated in the 

 direction of the longitudinal axis of the spine, and have evenly convex 

 and highly polished surfaces. On the aboral side the granules rise into 

 cones directed distally, the apex of the cones being almost or quite 

 above the distal edge of the base. The granules and cones are rather 

 well separated from each other, and the space between them is occu- 

 pied by a sort of loose spongy felting of rather coarse glassy anas- 

 tomosing hairs. The neck of the spines is usually, though not always, 

 distinct. It is from one-half to quite as long as the collar, shows only 

 slight indications of the granules, and is highly polished, lacking the 

 felted covering. The collar is somewhat more than 1 mm. in length, 

 cylindrical, and very finely striate, the striations being narrow, high, 

 and well separated, with a finely serrate crest. In occasional spines, 

 somewhat more tapering than the others, the features of the collar 



