122 Br. 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, Edrioaster levis. 



The conclusion, then, is that in Edrioaster lig^hyi the bend of 

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

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

 is solar, and none is recurved. In JE. hichianus the rays of the 

 only known specimen have the same arrangement. The same is 

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

 although Dr. Ruedemann says that one of the rays (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 right anterior ray 

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

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

 holotype of Leletodiscus dtcksoni all rays are contrasolar. The facts 

 are summarized in the annexed table. 



S = solar ; C = contrasolar ; E = straight. 



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

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



For the whole of their length the radial grooves are fl.oored 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 



