732 THE CRINOIDEA CAMERATA OF NORTH AMERICA 



its fellow of the same ray, the opposite side against the large interradial 

 plate, the lower face resting upon the radials. The second distichal trigonal, 

 very small, not larger than the costals, the two of the same ray together 

 formmo- a triangle, from the sloping sides of which the arms are given off, the 

 lower arm plates resting partly upon the distichals. Arms two to the ray, 

 divergent, rapidly tapering at the base, and rather slender above ; they are 

 biserial from their origin, and the proximal row of arm plates takes part in 

 the calyx. First plate of the interradial series very large, its lower portion 

 constituting a part of the dorsal cup, the upper part entering into the 

 ventral disk; it bends abruptly inward at two thirds its height, forming 

 a sharp edge along the margin. The lower end of the plate deeply wedged 

 in between the radials, the middle portion resting against the sides of the 

 distichals, the inflected upper end against the covering plates of the ambu- 

 lacra. This plate at the four regular sides is followed by two rows of inter- 

 ambulacral plates, generally arranged three and two, of which the upper 

 row abuts against the orals. The anal side has from ten to twelve plates 

 of irregular arrangement. Venti'al disk depressed hemispheric, the plates 

 tumid, with a small tubercle in the middle. Orals excentric and asymmetrical, 

 the posterior one wider than long, but not larger than the others. Ambu- 

 lacral plates much smaller than the surrounding plates ; the primary ambu- 

 lacra roofed by three series of plates, the two outer ones consisting of short, 

 transverse pieces, separated by a few elongate plates. The covering pieces 

 of the secondary ambulacra much smaller, and separated by one or two 

 large interaxillary pieces ; they are composed of two rows of regularly alter- 

 nating plates. Anus almost central. Column round, so far as observed ; 

 the axial canal pentagonal. 



Horizon and Localify. — Niagara group ; Decatur and Wayne Cos., Tenn. 



Types in the Mineralogical Museum at Breslau, Germany. 



Marsupiocrinus striatus "W. and Sp. (nov. spec). 

 Plate LXXV. Figs. 17, 18. 



A little larger than the preceding species, sometimes attaining a width of 

 6 cm. Calyx twice as wide as high, height of the dorsal cup about equal to 

 that of the disk. Dorsal cup truncated to near the middle of the radials, 

 then abruptly spreading upwards, the upper end slightly curving inward. 

 Plates densely covered by fine striae passing from the radial facets out to the 



