418 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



distributed all over abactinal surface, as in Dipsacaster (not absent 

 from midradial line or center of disk) , single, 5 or 6 about each plate. 



Marginal plates of the two series corresponding, with unusually 

 deep fasciolar channels separated by thin high ridges, each of which 

 is composed of the elevation of a combined superomarginal and infero- 

 marginal plate and is thinner than the intervening channels. The 

 height of this ridge above the bottom of the channel equals about one- 

 half the dorsoventral dimension of the combined marginal plates. 

 Superomarginals forming a rounded bevel as in Tethyaster subinermis, 

 covered with short, clavate, papilliform spinelets, becoming slenderer 

 on edge of grooves. Spinelets in grooves very numerous and delicate. 

 Superomarginals, about 80. 



Inferomarginals projecting slightly beyond superomarginals on 

 outer part of ray, and forming a rounded bevel to actinal surface, being 

 about one and one-half times wider than upper series. They are 

 covered with a transverse series of 2 to 5 flat, lanceolate, sharp, 

 appressed spinules and numerous shorter, slenderer, slightly flattened, 

 blunt spinelets, which are very much longer than those of supero- 

 marginals. The spinelets hning the deep f ascioles are similar to those 

 of upper series. 



Actinal interradial areas fairly large, but rather abruptly narrowing 

 at base of ray, along which two series of intermediate plates extend 

 two- thirds of its length, while one series continues nearly to the extrem- 

 ity. Rather deep channels lead from the marginal fascioles to the 

 f ascioles between adambulacral plates, these being separated by single 

 rows of intermediate plates. The marginal and adambulacral plates do 

 not correspond, however. At the base of furrow the latter are slightly 

 more numerous, while in the middle third, the former; distally they 

 correspond. The high keel of the intermediate plates which forms 

 the ridges between the channels is covered with spinelets, directed 

 toward ambitus, and similar to those of inferomarginals. 



Adambulacral plates astropectinoid, with an acute furrow angle, 

 bearing a compressed blunt saber-shaped spine, and *m either side of 

 this, two strongly compressed rather slender blunt spines. Some- 

 times a third is added, making the total 5 to 7. Surface of plate with 

 5 to 7 more cylindrical, slender, blunt spines, one forming a series with 

 the second lateral furrow spines, the rest disposed in about two longi- 

 tudinal series belund this, the laterals of the first series often standing 

 on margin and making on either side the supernumerary furrow spines. 

 The plates are wider than long, well spaced, with a shallow channel 

 between, over which extend several small terete spinelets belonging 

 to the transverse margins of plates. First two plates much com- 

 pressed. 



Mouth plates prominent, densely covered with spines, increasing 

 in length toward inner end of plate, where, directed over actinostome, 



