1914 122 F. A. Bather — Studies in Edrioasteroidea. 



The only certain exceptions to the normal arrangement are 

 E 15900 and E 16173, which have the rays all solar; but these, 

 on account of yet other features, are to be separated as a distinct 

 species, Edrioader levis. 



The conclusion, then, is that in Edrioaster bigsbyi the bend of 

 the right posterior ray is solar and recurved on the interambnlacrum, 

 that of all the others contrasolar. In E. levis the bend of all rays 

 is solar, and none is recurved. In E. buchianus the rays of the 

 only known specimen have the same arrangement. The same is 

 apparently the case in E. saratogensis llnedemann, 1912. For 

 although Dr. Ruederaann says that one of the raj^s (inferentially 

 the left posterior) is contrasolar, this is borne out only by his own 

 restoration of a specimen in which that ray is not preserved (pi. iii, 

 fig. 3). In his tig. 2 the proximal tract of the light anterior ray 

 has a slight contrasolar curve ; but all other rays in all figures are 

 solar or straight in that region. In Dinocystis barrojsi and in the 

 holotype of Lebetodiscus dichoni all rays are contrasolar. The facts 

 are summarized in the annexed table. 





Proximal. 



Distal. 





I. 



II. 



III. 



IV. 



V. 



I. 



II. 



III. 



IV. 



V. 



Edrioaster bigsbyi A . . 



S 



c 



s 



S 



c 



c 



c 



c 



c 



s 



„ B. . 



s 



c 



R 



S 



c 



c 



c 



c 



c 



s 



c. . 





? 



? 



? 



? 



c 



c 



c 



c 



s 



E 15930 



c 



c 



s 



s 



c 



c 



c 



c 



c 



s 



E 16054 



? 



? 



? 



s 



c 



c 



c 



c 



c 



s 



E 16172 













c 



c 



c 



c 



s 



E. levis — 























E 15900 



s 



c 



s 



s 



s 



s 



s 



s 



s 



s 



E 16173 



s 



? 



s 



s 



s 



s 



s 



s 



s 



s 



E. buchianus .... 



R 



K 



s 



s 



s 



s 



s 



s 



s 



s 



E. saratogensis . . . 



s 



s 



R,S 



s,c 



s 



s 



s 



s 



s 



s 



Lebetodiscus dicksoni 



c 



c 



R 



c 



c 



c 



c 



c 



c 



c 



Dinocystis barroisi . 



c 



c 



C 



c 



c 



c 



c 



c 



c 



c 



S = solar; C — contrasolar; 11 — straight. 



Floor-plates. — The main description applies to E. bigsbyi, especially 

 to specimen A ; the peculiarities of E. levis are noted later. 



For the whole of their length the radial grooves are floored by 

 a double series of alternating plates, which meet in a zigzag median 

 suture. These floor-plates are elongate at right angles to the median 

 line of the groove, the width of each plate being less than one-third 

 (ca. *28) of its length. Their outer margins are convexly curved; 

 their abutting margins are straight (PI. X, Fig. 4). The plates rise 



