1040 DK. J. W. ORBaORY ON THl CLASSIPIOATION [Dec. 15, 



Bohm has founded the genus OpJiiopege on the type species of 

 Aganaster [2 a. p. 159]. 



The genus Qhokister of Worthen and Miller [19. pp. 328-329, 

 pi. sxxi. fig. 4] appeal's to bo allied to Acjmmster, but the structure 

 of the ambulacral ossicles is unknown. 



Family 4. N Y H as T E n I D iE. 



Diar/nosis.- — Streptophiurse with well-developed vertebral ossicles, 

 and with very flexible, contorted, unbranched arms ; there are no 

 external arm-plates, tlie integument containing granules only. 



Distrihuiioii. — Keolcuk and Burlington Stages, Lower Carboni- 

 ferous, Iowa and Illinois. 



Genus Ontciiastbr, Meek & Worth. 



Ty2->e speeies.—Onyeliaster flexilis. Meek & Worth. [Proc. Acad. 

 Nat. Sci. Phil. 18G9, p. 83; 11. pp. 520-528; 11 «. p. 510, pi. xvi. 

 %■ 3]. 



Eemarls. — This interesting genus has hitherto been placed, 

 among the Euryalida;, of which it has been regarded as the best 

 knowji fossil re]n-esentative. As Prof. Bell, however, has re- 

 marked, Meek and Worthen's clear figures of the vertebral ossicles 

 show that tlie articular surfaces are Streptospondyline and not 

 Cladiophiuroid. 



Family 5. Etjoiad iiDjE. 



Diacpiosis.- — Streptophiiu'ie with contorted branching arms. 

 There are five pairs of largo plates (? radial shields) on the abacti- 

 nal side. The madreporite is large and dorsal in position. 'L'ho 

 arms have no oxtornal arm-plates, but are covered by a granular 

 iiih'gument. Ambulacral ossicles primitively ytrepto.spondylino. 



Genus Euoladia, II. Woodward, 1869 [18]. 



Tyj)e species. — Encladia jolinsoni, H. Woodward, Ldwer Ludlow, 

 near Dudley. 



Itemarlcs. — The affinities of this magnificent Starfish have been 

 left in some doubt owing to the absence of information as to the 

 structure of the vertebral ossicles. It has generally been assigned 

 to the Euryalida), owing to its granular integument and branching 

 contorted arms. Fortunately, however, I have found the articular 

 surface of the vertebral ossicles exposed on the side of the block 

 of limestone containing the specimen. The articulation is truly 

 Streptospondyline of a rather primitive type (fig. G a, b, p. 1041). 

 The ossicle is egg-shaped in section, with the broader end above. 

 Two broad muscle-fields occur, one at each of the quadrants of 

 the ossicle. On the central line just above these there is a small 

 knob. The upper half of the ossicle is occupied by two pairs of 

 depressions separated by simple ridges. 



