700 THE CEINOIDEA CAMERATA OF NORTH AilERICA. 



'Platycrinus peculiaris W. and Sp. (nov. spec). 

 Plate LXVIII. Figs. 7a, h. 



Of medium size. Calyx one third higher than wide ; the dorsal cup 

 about as wide as high, obconical at the base, cylindrical along the radials ; 

 the plates rather thin. The ornamentation of the plates cannot be accu- 

 rately ascertained in the specimens, but the surface shows traces of obscure 

 ridges passing down diagonally from the radial facets to the lower angles of 

 the radials, and from the column w]> to the angles of the basal cup, which 

 suggests that the surface was marked in a similar manner as in P. scidptus, 

 but perhaps less distinctly. The sutures slightly grooved. 



Basal cup basin-shaped, its height equal to one-half the length of the 

 radials, gradually expanding upwards, and slightly beveled around the upper 

 margins ; the column facet small, somewhat projecting, and the interbasal 

 suture lines distinct. Radials subquadrangular, nearly as wide as long, the 

 median line sometimes a little elevated, the lower faces very slightly convex; 

 the lateral faces almost parallel, the sloping upper faces wide and forming 

 broad interradial notches, of which that at the anal side is deeper than the 

 others. Facets extremely small, not occupying more than one fourth the 

 width of the plates, and often considerably less. Costals small, as long as 

 wide, occupying the entire facet. Distichals narrow, almost as long as wide, 

 all in sutural contact with adjoining interradial plates, and as such constitut- 

 ing a part of the calyx, although having the form of free arm plates. Ven- 

 tral disk hemispheric, slightly bulging at the anal side, studded with numerous 

 small, nodose pieces, of very nearly equal size. The orals unusually small ; 

 the ambulacral pieces on a level with the other disk plates, and of the same 

 size ; they are very regularly arranged, and branch upon the disk. The 

 interradial plates consist of three rows of three each ; those of the first row 

 are perfectly flat, and interbrachial in position, the others being nodose and 

 interambulacral ; the middle plate of the first row very large, oblong and 

 heptagonal, the two at the sides as long, but very much narrower. Anus 

 excentric, at the top of a small protuberance. Number of arms unknown. 



Horizon and Locality. — Lower Burlington limestone ; Lake Valley, New 

 Mexico. 



Tiijje in the collection of Wachsmuth and Springer. 



