PALEONTOLOGIC CONTRIBUTIONS 49 



adambulacrals to have been more closely arranged,, broader and 

 thicker disks ; and also the ambitals and ambulacrals appear to have 

 been relatively thicker. 



Urasterella Stella nov. 

 Plate 12, figures i and 2; plate 13, figure 1 



Description. Rays short, rapidly tapering and angularly convex 

 abactinally. Disk formed only by the united bases of the arms. 

 The ossicles of the disk are all spinose, small, granular, indistinctly 

 arranged in three or four concentric circles. Those of the rays 

 are arranged extremely regularly in columns in quincunx, giving the 

 surface a striking similarity to a knitted texture. The crest, of 

 the ray is formed by a single column, the radial plates, which are 

 a little longer than the other ossicles. The sides are formed by 

 three columns each of equal subquadrangular plates, the column 

 adjoining the radial plates on either side not reaching to the tips 

 of the rays. All ossicles of the rays are furnished each with one 

 long unarticulated spine or rod. These fail to appear in the squeezes 

 from which the photographs are taken except on the lowest column 

 where they are directed horizontally. The madreporite has not been 

 found. The actinal side shows very broad ambulacral grooves with 

 subrectangular ambulacral plates and relatively small podial open- 

 ings, excavated at the forward exterior angle. The adambulacral 

 plates are narrow, coin-shaped, arranged on edge, the columns 

 terminating in the ossicles of the oral armature, which, so far as 

 discernible, are small and subtriangular in shape. The adambulacral 

 plates are flanked on either side by a row of small semielliptic 

 ambitals bearing short, stout central rods. 



Measurements. The radius of the rays (R) is 10.5 mm long, 

 that of the disk (r) about 2.5 mm, and the rays are about 2.3 mm 

 wide at their base. 



Horizon and locality. The specimens were collected by Mr D. D. 

 Luther in the Middle Grimes sandstone (Portage group), about 

 3^2 miles northeast of Naples, near William Harrington's residence. 



Remarks. The material consists of one specimen showing the 

 abactinal side and another retaining both the actinal and abactinal 

 sides in the specimen and counterpart. This species is distinguished 

 from the Chemung type of Urasterella by the shorter, stouter rays, 

 smaller number of columns on the abactinal side, and on the actinal 

 side, in the shape of the ambulacral and adambulacral plates, which 

 are narrower. 



