A/anual of the Paleontology of the Cincinnati Group. 



137 



plates wanting ; ambulacral furrow narrow ; ambulacral plates in two 

 rows; adambulacral plates small, flattened, sub-circular, twenty-five or 

 thirty in number, gradually decreasing in size from apex to base of 

 rays ; oral plates ten, each somewhat triangular ; dorsal surface of rays 

 with three (?) rows of plates, extending over the adambulacral row on 

 ventral surface. (Jour. Cin. Soc. Nat. Hist., vol. 2, p. 11^ as Palceaster 

 harrisi. 



Locality. — Waynesville, O. 



Remarks. — Although originally described as a species of Palceaster 

 the distinct assertion that the marginal plates are wanting seems to 

 take it out of that genus, where the marginal plates is a chief charac- 

 teristic. We have therefore, ventured to put it into Stenaster. 



Class 2. — OPHIUROIDEA. 



To this class belong the " brittle-stars," or those forms of star-fish 

 that lose their arms readily on being disturbed. It may be denned as. 

 follows : 



Body stellate, consisting of a central disc containing the viscera,, 

 and of elongated, often flexible arms, which are sharply defined from 

 the disk, do not contain prolongations of the alimentory canal, and 

 are without open, ambulacral grooves on the under surface* 



Genus 1.— PROTASTER Forbes, 1849. 



" Body circular, covered with squamiform plates; genital open- 

 ings in the angles of junction of the arms beneath; arms (simple) 

 formed of alternating ossicula. (Mem. Geol. Sur. Gt. Britain , decade 

 1, pi. 4.) 



Remarks. — The above is the original description given by Forbes. 

 Salter in 1877 (Ann. and Mag. Nat. Hist., 2d ser. vol. 20, p. 325), 

 re-defined it as follows: 4 'Arms elongated, extending much beyond 

 the circular, closely reticulate disc; the arms are composed of two 

 rows of deeply sculptured plates, spinous at the edge, and below of 

 two rows of elongated ambulacral ossicles, bordered by a row of large 

 spinous plates ; the basal ossicles of the ambulacra, bordering plates 

 and disc, combined to form a petaloid mouth below." Another 

 feature still is the presence of bunches of lateral spines on the plates 



* Nicholson, Ibid. vol. 1. p, 399. 



