8 PBOCEEDINGS OF THE NATIONAL MUSEUM vol.80 



All the oculars are exsert, II and III widely so, IV rather less 

 widely, I still less widely, and V barely exsert. The oculars are very 

 small, chevron-shaped, each with five very small tubercles. 



Near the oculogenital ring each interambulacral plate bears a 

 prominent central tubercle and a few small peripheral tubercles. 

 These last on the third or fourth plate beyond the genital form a 

 complete row and vary somewhat in size, those at the angles of the 

 plates being the largest. Just above the ambitus those near the outer 

 edge of the plate rapidly increase in size, and at the ambitus others 

 beyond these also increase in size so that when viewed from above 

 the inner two-thirds or half of the interambulacral areas is seen to 

 bear two rows of large tubercles, while the outer third has four 

 rows; and at and just below the ambitus there is a short row of some- 

 what smaller tubercles beyond each of the outer rows. On the actinal 

 surface of the test these six rows rapidly converge, as a result of the 

 broadening of the poriferous areas, and the tubercles become smaller. 

 Two-thirds of the distance from the ambitus to the peristome the 

 intermediate rows on each half of the interambulacra come to an 

 end, and from that point the two central rows, and at some distance 

 from them the two outermost rows, continue parallel to the peristome. 



The ambulacral plates each bear a prominent tubercle, which 

 slowly increases in size from the oculogenital ring to the ambitus; 

 on the oral side of the test these tubercles rapidly decrease in size, 

 and the two lines of tubercles converge; slightly more than half- 

 way between the ambitus and the peristome the now very small 

 tubercles form two parallel rows close together and run to the 

 peristome. 



There are 8 to 11 (usually 9 or 10) pore pairs in an arc both at 

 the ambitus and near the oculars. 



The oral surface of the test (pi. 2) is flat, and is only very slightly, 

 if at all, concave in the longer axis. The peristomal area is pentag- 

 onal with double angles. The radius to the point of an angle (on 

 the ambulacral-interambulacral border) is 11.5 mm., and the radius 

 to the deepest (inner) portion of a poriferous area is 10 mm. 



On the oral surface the poriferous areas gradually and regularly 

 broaden to a maximum width of 5.5 mm. two-thirds of the distance 

 from the ambitus to the peristome. From that point the outer bor- 

 der curves broadly downward and inward, but the inner border 

 curves only very slightly. At their widest point the poriferous 

 areas are about three- fourths as broad as the interambulacral areas 

 separating them. 



At the ambitus the primary spines are from 20 to 25 mm. long, 

 the lower more or less strongly flattened, especially on the lower 

 side. Though the lower side is slightly and evenly convex, the 



