Contributions to Palaeontology. 31 



The marginal plates have about the same form, and are about as 

 numerous as they are in P. speciosa. The adambulacral plates are 

 arranged with their length across the rays. The oral plates are very 

 prominent. The space between the marginal plates and the oral ones 

 is filled. with numerous small pieces. The ambulacra! grooves are 

 narrow. Ambulacral ossicles unknown. 



The dorsal side is covered with small conical pieces, which give it 

 a coarsely granular appearance. The madreporiform tubercle is 

 prominent, conical and longitudinally striated. 



This species is distinguished from P. speciosa by its narrower rays, 

 more contracted bod}-, and smaller dorsal plates. 



We have examined two specimens belonging to Mrs. Haines, which 

 were found in the upper part of the Cincinnati Group, near Richmond, 

 Indiana, one of which shows the dorsal side and madreporiform 

 tubercle, and the other the ventral side, from which part of the fore- 

 going description was drawn. The specimen figured shows the ventral 

 side, and was collected by D. R. Anderson, near Waynesville, Ohio, in 

 the upper part of the Group, and is now in the collection of C. B. Dj^er. 



Protaster flexdosus, n. sp. (Plate II., fig 1, dorsal side; fig. lo, 



ventral view). 



[Ety. — Flexuosus, full of turnings.] 



The disk is composed of very thin, small plates, the order of arrang 

 ment of which is not determined. The specimens examined difi'er in 

 size, and show the disk varying in diameter from :| to | an inch. The 

 rays were very flexuous when living, and are found winding and turn- 

 ing and thrown in diflerent directions, in difi'erent specimens. 



Four series of plates are seen upon the dorsal side of each ra}' near 

 the disk. The two inner series form an angular ridge, each plate is 

 concave at the uniting surface, the arrangement is alternate, and the 

 appearance, therefore, of the top of the ray, is something like the al- 

 ternate arrangement of two series of hour-glasses. The outer series, or 

 marginal plates, are spinous, the spines directed toward the point of 

 the rav. A weathered ray shows three series of pores — one row be- 

 tween the inner series of plates, and one between the marginal plates 

 and inner series, upon each side of the ra^'. The plates are a little the 

 longest in the direction of the length of the ra}^ and in this direction 

 there are about four to the line. The rays cross the disk on the dorsal 

 side, and unite near the center of it, but the specimen figured, Plate 

 II., fig. 1, has this part of the rays removed. Plate II., fig. la, illus- 

 trates the ventral side of a specimen, which is too indistinct to show 

 the arrangement of the plates. Small pieces, showing the ventral side 



