MELOCRINID^. 315 



larj disticbal followed by 3 X 2 palmars and two arms, upon the other three 

 fixed distichals, which support one arm. There are three primary arms, tw^o 

 and one, to the ray; two of the simple arms facing the anal interradius. 

 Arm openings directed obliquely upwards, less projecting and smaller than 

 usual in the genus. Interbrachials : 1, 1, 3, 4 ; the first large, rather angular 

 below, broadly truncate above, the upper sides a little wider than the lower ; 

 the second almost as large as the first, with a long transverse node. The 

 three plates of the third row much smaller and provided with elongate nodes. 

 The plates of the fourth row, which occupy the arm regions, are small and 

 highly convex, their upper faces pierced by the lower part of the slits. The 

 interambulacral plates consist of five large cuneate plates, of which the three 

 middle ones are larger than the others -, the sides of the outer ones excavated 

 to form the slits, which are quite large in this species. The anal interradius 

 has a few additional plates in the disk, which connect wath the anal tube. 

 Interdistichals four to the arm regions, arranged in two rows, followed by 

 three cuneate interambulacral plates, with two slits, while there are four slits 

 above the interbrachial spaces. Orals large, all of similar form and size, 

 surrounded by good sized radial dome plates of a first, second, and third 

 order. Anal tube almost central, its base formed of rather large convex 

 plates. 



Horison and Locality. — Upper Helderberg group ; Clark Co., Ind. 



Types in the collection of Victor W. Lyon, Jeffersonville, Ind. 



Remar'ks, — This species is readily distinguished from all others of this 

 genus known to us by the grotesque style of its ornamentation. 



Dolatocrinus canadensis Whiteaves. 

 Plate XXV. Figs. 7a, h. 



1887. Whiteaves; Geol. and Nat. Hist. Surv. Canada; Contrib. to Can. Palseont., Vol. I., p. 99, Plate 12, 

 figs. 3, 3tf. 



Of the type of Dolatocrinus Marshi, but with a different arm formula. 

 Calyx small, much wider than high. Dorsal cup broadly and shallowly 

 basin-shaped, slightly depressed along the radials, and more conspicuously at 

 the basals. Ventral disk lower than the dorsal cup ; hemispherical ; the 

 central portions slightly tumid. The ornamentation of the dorsal cup con- 

 sists of numerous parallel ridges, passing out to the sides of the plates, and 

 meeting those of adjoining ones. The rays along their median lines followed 



