38 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



form organ, convex and traversed by coarse ridges radiating from 

 a i^oint between the center and adcentral edge. A few spinelets sur- 

 round it. 



Marginal plates thin, the superomarginals the higher. Second 

 superomarginal about as long as high, but the succeeding i'our are 

 longer than high, and the seventh or last about as long as high. Each 

 bears on the upper distal corner a slender, prominent, sharp spinule 

 usually bent transversely across the smooth abactinal integument. 

 The second plate has a shorter companion spinule. The longest 

 spinule (2 mm.) is on the fifth plate. 



Inferomarginal plates conspicuously lower than superomarginals 

 and hence proportionately longer than high. Second plate corre- 

 sponding to second superomarginal is shorter than the rest. These 

 plates do not encroach upon actinal surface. No spines. 



Cribriform organs very prominent, wider than high, with slightly 

 convex upper border, and leaving only a very narrow bare area on 

 distal edge of the plates. The organs comprise therefore practically 

 all the surface of each interradial pair of supero- and inferomarginal 

 plates. The spinelets are blunt, slender, very uniform in size, and 

 arranged in vertical series. Those of the first or marginal vertical 

 series are webbed. No others are. 



Terminal plate prominent, crescentiform, the rounded sides cover- 

 ing the edges of the last marginals. There are 5 terminal, promi- 

 nent, sharp spinules; 3 of these form a triangle in the end of 

 plate, surrounding the terminal papilla, and one stands laterally on 

 the upper edge of plate. 



Adambulacral plates longer than wide and with a concave margin. 

 Each plate bears at the adoral end 2 sharp marginal spinules some- 

 times slightly curved and compressed at base, these occupying about 

 half the furrow margin of each plate. 



Mouth plates very prominent actinally, the free surface sloping 

 steeply to median suture, which is wide and lanceolate in form. Each, 

 pair of plates bears an unpaired spine at the inner angle where the 

 2 plates join, and widely spaced from this, 4 tapering, sharp, 

 marginal spines are borne on the concave margin opposite the first 

 tube foot. 



Actinal intermediate areas moderate, the plates loosely joined in 

 irregular interradial columns. Six to 8 of the plates on either 

 side of the double interradial series bear a single spinelet similar to 

 those of cribriform organ. 



Tube feet large, without calcareous particles in the walls. Dorsal 

 wall of the stomach with numerous simple, straight, rather large 

 microscopic rods, with occasional irregular and Y-shaped ones. The 

 length of these rods varies about as the diameter of the plates in the 

 dorsal integument. 



