EEVISION OF PALEOZOIC STELLEEOIDEA. 97 



DEVONASTER, new genus. 

 Plates 11 and 12. 

 Palseaster (part) of Authors. 



Xenaster (?) or new genus Gregory, Geol. Mag., dec. 4, vol. 6, 1899, p. 346. 

 Devonaster Schuchert, Fossilium Catalogus, Animalia, pt. 3, April, 1914, p. 14. 



A characteristic starfish of the American Devonic. 



Generic cliaracters. — ^Rays five, stout, tapering rapidly. Disk 

 large, with small interbrachial arcs. 



Abactinal area of rays with prominent columns of radial supra- 

 marginals and less prominent inframarginal plates, all of which 

 bear numerous small pustules. The radial columns are completely 

 separated from the supramargmals by a great abundance of very 

 small, conical, irregularly arranged, accessory plates which in the 

 proximal region may also force apart single plates of these columns. 

 The supramargmal columns of adjoining rays nearly meet in the 

 axillary areas a short distance mside of the margin, at which level 

 the radial columns also cease. Inside of the area bounded by the 

 proximal plates of the radial and supramargkial columns, the disk 

 has numerous small accessory plates Hke those of the rays. In the 

 center of the disk is a plate somewhat more prominent than those 

 surrounding it, and just mside of the adjoining proxunal supramar- 

 ginals is a small but distinct plate interradial in position. 



Ambital accessory plates abundantly developed between the 

 marginal ossicles in the axillary areas. These plates are like the 

 other accessory plates and do Jiot extend beyond the third or fourth 

 proximal mframarginal pieces, where the ambital areas cease and 

 the supramarginal ossicles come to lie more and more completely 

 over the inframarginals. 



Madreporite flat or concave, situated between two proximal 

 supramarginal ossicles and outside of one of the small interradially 

 situated plates. 



Inframarginal pieces large and thick, increasing rapidly in width 

 proximally, so that the two wedge-shaped proxunal plates are nearly 

 three times as wide as long. The plates are pustulose, and the proxi- 

 mal ones bear several slender spines. 



Adambnlacral plates more numerous than the inframarginals, 

 continuing around the axillary interbrachial plates, in front of 

 which the columns meet in two triangular and enlarged adambn- 

 lacral oral armature plates. Each piece bears two short, obtusely 

 pointed spines. 



Ambulacral grooves narrow and deep, either straight or very slightly 

 petaloid. Ambulacral plates equahng in number the adambulacrals 

 and arranged in directly opposed, closely adjoining columns. Podial 

 openings in two columns through the sutures in the lateral part of 

 the furrows. 



