REVISION OF PALEOZOIC STELLEEOIDEA. 181 



measures: R = 10 mm., r = 2.5 mm., R = 4r. Width of rays at base 

 in mature examples from 7 mm. to 8.5 mm. 



Rays at maturity very long, depressed subcylindrical in outline, 

 slender and tapering slowly. Disk very small, formed by the united 

 inner ends of the rays. 



Abactinal area reticular, consisting of very numerous, highly 

 conical, stellate plates, the radial columns and the plates of the disk 

 most prominent, while the other ray plates (supramarginal and 

 ambit al) are smaller and irregularly triangular in form. All plates 

 are more or less drawn out into stout, blunt, nonarticulating spines 

 which are best preserved along the sides of the rays. On the disk 

 the ossicles are arranged in a few concentric rows while on the rays 

 they are in columns and in quincunx. Near the base of a ray in the 

 largest specimen there are about 13 columns, diminishing to about 

 4 at the distal ends. 



Madreporite of medium size, lobate, radially crenulostriate, situ- 

 ated between two adjoining rays and about midway between the 

 margin and center of disk. 



Adambulacral plates slightly overlapping the ambulacral columns, 

 diminishing in size distally, coin-shaped, arranged on edge, and vary- 

 ing in different specimens from 60 to 110 in each range. In the 

 youngest known example there are about 20 plates in a column. 

 Each piece bears three or four short, finger-shaped, articulating 

 spines, two or three outwardly disposed, and one placed near the 

 inner base between adjoining plates. Along the outer margin of 

 the adambulacral plates and abactinally to the thick finger-shaped 

 spines there is a row of long, slender, flattened and longitudinally 

 grooved spines, two to each ossicle. Orally the coin-shaped adam- 

 bulacral plates are somewhat modified, stand less erect and terminate 

 in pairs of subquadrangular oral armature pieces. 



Ambulacral grooves wide, shallow, and furrowed medially by a 

 narrow angular gutter. Ambulacral plates of adjoining columns 

 opposite or very slightly alternating, the pieces narrow, equaling 

 in number the adambulacrals, slightly overlapping each other 

 proximally and partially interlocking in the medial gutter. The 

 ambulacral plates continue in undiminished size to the compara- 

 tively small mouth, are highly convex and club-shaped, with the 

 attenuated ends laterally disposed. The podial openings are between 

 the attenuated ends of adjoining plates. 



Locality and formation. In the Richmond formation at Richmond, 

 Indiana (type-locality), and in the vicinity of Waynesville, Ohio, 

 where Mr. Harris secured six more or less mature and three young 

 individuals, besides numerous fragments. A ray of this species 

 was found by Mr. U. P. James near Dayton, Ohio. In the Gurley 

 collection of the University of Chicago there is a young specimen 

 (No. 10978) from near Ridgeville, Warren County, Ohio. 



