S PEOCEEDIKGS OF THE NATIONAL MUSEUM vol.72 



slight truncations on the margin ; a marked angulation on the ambitus 

 marks the outer corners of each of the depressions at equal distances 

 from the posterior center, and each angulation is continued in a very 

 faint ridge up over the test. Dimensions of the holotype: Length, 

 41 mm. ( ? ) ; width, 38 mm. ; height, 20 mm. Dimensions of the para- 

 type shown in figure 6: Length, 39 mm.; width, 3Y mm.; height, 

 18 mm. 



The petaloid portions of the ambulacra are rather narrow and the 

 areas between the pore bands are slightly upraised; the petals are 

 broadest apically and become narrow lanceolate toward the lower 

 extremity where the pore bands almost touch ; below the ends of the 

 petals the ambulacra are very narrow, but they broaden out gradually 

 to the ambitus, beyond which on the base they gradually narrow down 

 again to the floscelles which broaden out conspicuously. In the petals 

 the pores are small, and the pairs are connected by very narrow fur- 

 rows, narrower than the intervening ridges; the outer pore of each 

 pair is only slightly more elongated than the inner one ; the furrows 

 are very closely spaced and trend obliquely downward away from the 

 centers of the petals. Below the petals a single row of pores can be 

 faintly seen on each side of the ambulacral areas near the outer 

 borders, these pores being situated on or near the sutures separating 

 the plates, and the pores can be traced all the way to the floscelles. 

 Each floscelle consists of a pair of large triangular x^lates next to 

 the oral opening, followed outwardly by two series of five to nine 

 narrow plates, one series on either side of the median line, followed 

 by several broader plates of irregular shape and size, which form the 

 transition into the plates of the narrow ambulacral area. As in other 

 nearly related species all the plates of the floscelles above the triangu- 

 lar plates bear pores at their outer ends which are arranged roughly 

 in the form of an arch convex outward; on the two postero-lateral 

 and the anterior floscelles the arched arrangement includes 6 to 8 

 pores on each side of each floscelle with a group of 3 to 5 pores some- 

 what sunken below the crest of the arch; the two antero-lateral 

 floscelles are narrower and include 10 or 11 pores on each side of the 

 arch, with no central group of pores above, leaving the arch open 

 and slightly flaring at the top. Some of the long narrow plates bear 

 pores near their inner ends, and a pair of pores occurs one pore on 

 each of the large triangular plates next to the oral opening. 



The ambulacral plates in the petals are long horizontally, very 

 narrow and numerous. Below the petals the ambulacral plates are 

 broader and vary in shape and size on different parts of the area. 

 The interambulacral plates are much larger, the largest ones being 

 about two and one-half times as long horizontally as they are wide. 

 The whole upper surface with the exception of the madreporite is 

 densely packed with small tubercles set in deep small areolas; a 



