KE VISION" OF PALEOZOIC STELLEROIDEA. 143 



"The ambulacral grooves are narrow and deep, as shown by the 

 sharp ridges on the back of the specimen. The small dorsal plates 

 which cover the ambulacral pieces are exfoliated in some places, 

 and show two rows of ambulacral plates coming evenly together 

 and forming the sharp ridge.'' 



Original description of Palseasterina approximate, . " Pentagonal; 

 rays more slender than in P. speciosa; greatest distance from point 

 to point in the specimen figured 1.15 inches and breadth of the 

 body one-half inch; another specimen from the collection of Mrs. 

 M. P. Haines, of Richmond, Ind., measures from point to point 2.5 

 inches, and has a breadth of body of nine-tenths inch. 



"The [infra] 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. [This statement is somewhat in error. 

 The five prominent points around the mouth are each formed of one 

 large interbrachial plate and a pair of proximal adambulacrals.] The 

 space between the [infra] marginal plates and the oral ones [adambu- 

 lacrals] is filled with numerous small [accessory interbrachial] pieces. 

 The ambulacral 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 body, and smaller dorsal plates." 



Emended description. The holotypo of P. speciosa measures: 

 R = 33 mm., r 18 mm. The holotype of P. approximata measures: 

 R = 15 mm., r = 6.5 mm. 



Rays in young specimens slender distally, but with age they 

 become obtuse and very wide proximally and here merge into the large 

 disk. Interbrachial arcs very large. 



The abactinal area of disk and rays is bounded by columns of very 

 prominent inframarginal plates. Beginning at the apex of each ray 

 they are very small and globular, soon they become quadrate and 

 gradually shorter but wider, so that near the middle of each interbra- 

 chial arc they have a crowded appearance. In a full-grown specimen 

 there are about 50 and hi a half-grown example about 45 of these 

 plates between the distal ends of adjoining rays. In the distal region 

 these plates are rounded and nearly smooth but gradually become 

 granular and strongly convex, each with one prominent point for an 

 articulating spine, none of which, however, have been observed. On 

 the actinal side these inframarginals are also very prominent and 

 pustulose but here are flat. They are most prominent near the center 

 of the interbrachial arcs. 



50601 Bull. 88 15 10 



