REVISION OF PALEOZOIC STELLEROIDEA. 99 



acutely pointed at the extremity. Upper [abactinal] surface of 

 rays composed of three [radial and two supramarginal] ranges of 

 large, highly convex or tuberculiform plates which are nearly cir- 

 cular at the bases of the rays, becoming quadrate and widened to- 

 wards the extremities; separated from each other in the lower part 

 by numerous minute [accessory] plates or granules, which become 

 fewer near the middle of the ray, and before reaching the extremity. 

 The central portion of the disk is occupied by an elevated pentagon, 

 the angles of which are formed by the abrupt termination of the 

 central row of plates of each ray: the whole composed of very mi- 

 nute, highly convex plates, which vary in size, the larger ones pen- 

 tagonally arranged. The angles between the rays have a few [nu- 

 merous] small [accessory ambital] plates outside of the outer ranges 

 of tuberculose [supramarginal] plates on the upper side, uniting 

 with the inframarginal plates below [and not extending beyond 

 the third or fourth inframarginal proximal plate]. Madreporiform 

 tubercle distinct, situated lateraUy at the bases of the outer [supra- 

 marginal] range of large plates of two adjacent rays. Ventral sur- 

 face having deep ambulacral grooves, bordered by two ranges of 

 strongly tuberculose plates; the outer [infra] marginal range con- 

 sisting of 27 or 28 plates, besides a large, round [or elliptical], ter- 

 minal or axillary [interbrachial] plate; the others are wider than 

 long in the basal portion of the ray, becoming gradually shorter 

 towards the extremity where they are rounded. All the [infra] 

 marginal plates are visible from the upper [abactinal] side, and 

 usually appear as an additional range of plates on each margin of 

 the ray, making five with the three properly belonging to the upper 

 surface. Those of the inner range bordering the ambulacra (adam- 

 bulacral plates) are smaller than the marginal plates, about 38 to 

 40 in number; the basal or oral plates [oral armature] are triangular, 

 those of the adjacent rays uniting by their longer margins; and with 

 a single minute plate situated at these points. The plates of the 

 exterior surface, both upper and lower, present a granulose or stri- 

 ato-granulose surface which appears to have been produced by short 

 setae or spines; and at the angles of the rays the marginal plates 

 are armed by a few spines, which are as long or longer than the 

 transverse diameter of the plates. Ambulacra composed of a double 

 range of short, broad poral plates (ossicula), equal in number to 

 the adambulacral plates ; their outer ends excavated on the posterior 

 border, forming a comparatively large pore, just within its junction 

 with the adambulacral plate. There appears to have been [is] but 

 one range of pores in each set of ossicula, but these are large, dis- 

 tinct, and pass between [through and not between] the plates." 



The following additional description is that of Mr. Cole. The 

 surface of the axillary interbrachial plate "is granulose and bears 



