PLATYCEINID^. 661 



Horizon and Locality. — Base of Lower Burlington limestone ; Louisi- 

 ana, Mo. 



Type in the collection of Mr. Kowley. 



Remarks. — From the small size of the specimen, and the structure of the 

 ventral disk, we are inclined to believe that it represents a very youno- form 

 of P. hurlingtonensis. 



Platycrinus quinquenodus White. 

 Plate LXXI. Figs. 14a, b, c. 



1862. White ; Proceed. Boston Society Nat. Hist., p. 18. 



1881. W. and Sp. ; Kevision, Part II., p. 74 (Proceed. Acad. Nat. Sci. Phila., p. 248). 



Syn. P planobasalis Eowlet and Hake, 1891; Kansas City Scientist, p. 97, Plate 2, Fig. 1. 



Of moderate size. Calyx rather rapidly and evenly spreading from the 

 truncated base to half the height of the ventral disk ; the lower brachials 

 directed almost horizontally. Ventral disk as high as the cup, distinctly 

 convex, extended outward to the top of the distichals, and forming well de- 

 fined lobes, which give to the calyx a sharply quinquelobate outline. Plates 

 of the dorsal cup heavy and without ornamentation, except that the base is 

 marked by five rounded nodes, interradially disposed and directed down- 

 ward. Basi-radial and interradial sutures channeled. 



Basal cup deejj, fully two thirds the length of the radials, truncated at 

 the bottom, the sides gradually spreading. Eadials as long as Avide, wider 

 ■above than below, the median portions below the facets much the thickest; 

 the lower faces almost straight, the upper angles deeply truncated and 

 forming with the corresponding sides of adjoining plates deep notches; the 

 notch of the anal side considerably deeper, extending down to fully one 

 third the length of the plates. Facets semicircular, facing almost horizon- 

 tally, the upper end not notched, or only a very little. Costals pentangular, 

 the upper faces concave. Distichals nearly twice as wide as long, those of 

 the same ray in sutural contact laterally, the upper ones axillary. Structure 

 of arms unknown. Plates of the disk nodose, except the interambulacrals of 

 the anal side, which are barely convex. Orals very large, almost symmetri- 

 cally arranged ; the posterior one a little larger and wedged in between the 

 others. The plates of the disk ambulacra large and tuberculous, extending 

 out to the ends of the distichals and forming rigid tubular extensions. Inter- 

 ambulacrals three, the middle one twice as long as the two at the sides, but 

 without touching the orals. The middle plate of the anal side considerably 



