256 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



and increases similarly in size towartl outer edge where the granules are thimble- 

 shajiod or truncate cylindrical. Tiie unpaired ])late is not quite so large as that of 

 doi-sai series. Rather deep channels between plates. Terminal plate, cordate, con- 

 vex, broad end distally ; covered with short spinelets, two being thicker than the rest. 

 ' Adambulacral plates wider than long. They are short with a narrow transverse 

 suture, the plates having a crowded appearance. Furrow margin straight, and 

 plates generally oblong like some species of Tosia and Pcntagonaster. Armature 

 consists of two terete, tapermg, bluntly pointed spinelets on the furrow margin, one 

 slightly smaller than the other, the longest slightly shorter than width of plate. On 

 actinai surface are sLx or seven similar but sometimes sharper spinelets which 

 diminish in size as they recede from furrow, and are usually disposed in three 

 more or less regular longitudinal series (or oblicjue longitudinal), two spinelets 

 to each, and the spinelets unequal as in furrow series; spinelets of first and second 

 series often slightly longer than furrow series, the outermost shorter, about the 

 size of adjacent actinai intermediate spinelets. The spinelets form a fairly thick 

 chevaux-de-frise all along the border of the very narrow ambulacra! groove, resem- 

 bling that of Gephijreaster swifti. 



Mouth plates with a movable, recurved, conspicuous, lanceolate spine, which 

 has an obtuse inner end or base and a sharp outer glassy tip ; one to each pair of 

 plates; this spine is rather broad actinally, not much compressed, and nearly as long 

 as interradial dimension of plates. Each plate is a low isosceles triangle in shape, 

 the base being toward interradial suture. Along the straight furrow ijiargin are 

 five to eight spinelets similar to but often smaller than adambulacral spinelets, 

 and graduated in length from center toward either end of series, the inner being 

 shorter than outer. On surface of plates five to eight spinelets form an irregular 

 line at side of median spine. 



This recurved median spine or "tooth," which forms the principal character, in 

 addition to the unpaged marginal plates, of the family Odontasteridffi, is nothing 

 more than the very much developed median or odd marginal spine such as is found 

 in most species of Pseudarchaster, and in Gepliyreaster. In growing it is bent back- 

 ward over the surface of the mouth plates, and comes to lie wholly on the exposed 

 surface of the pair, the marginal spinelets encroaching upon the inner angle of the 

 combined plates. 



Actinai intermediate areas large. The plates are square and arranged in 

 regular series parallel to furrow, along which they extend three-fourths the length 

 of R (to fifth inferoinarginal). Plates bear a group of five to twelve radiating, 

 stout, short, tapering pointed spinelets (on some specimens much longer on middle 

 of plate), occasionally forming a fairly ornate rosette. 



Madreporic body rather small, situated midway between center and inner edge 

 of interradial plate; shape very broadly oval; striations coarse, irregular. 



Color in hfc: marginal plates orange; paxillar area lemon yellow. (Young 

 specimen.) 



Anatomical notes. — Anal aperture present. Intestinal coecum very large, con- 

 sisting of a small subcircular central portion and four main radiating divisions 

 the tip of each being smaller and bifid. Intestinal coecum ^\■ith its branches more 

 capacious than dorsal stomach (loss hepatic cceca). Aperture from intestinal ccEcum 

 into dorsal stomach wide. Dorsal stomach sharply dift'ercntiated from ventral. 



