314 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



Dolatocrinus Marshi, var. hamiltonensis W. and Sf. 



Plate XXV. Figs, 2a, h. 



A form very similar to D. Marshi occurs in the Hamilton group, which 

 we distinguish from the typical form as variety hamiltonensis. The basal con- 

 cavity is shallower and narrower, the radial ridges knife-like, and occupy the 

 median line of the plates instead of being keel-shaped and rising gradually 

 from the outer margins of the plates. The ventral disk is considerably 

 lower, and but slightly convex ; the orals smaller, the posterior one, which 

 is very short, is placed so as to form at the anterior side the base of the anal 

 tube. All plates of the disk covered by several well defined tubercles. 



Horizon and Locality. — Hamilton group, Bear grass quarries, Louis- 

 ville, Ky. 



T^pe in the collection of Mr. Victor W. Ljon, Jeffersonville, Ind. 



Dolatocrinus Lyoni W. and Sp. (nov. spec). 

 Plate XXV. Figs. 6a, h, c, d. 



Calyx rather large, considerably wider than high. Dorsal cup more than 

 twice as wide as high -, the basal portions deeply impressed, forming a broad 

 funnel-shaped cavity which includes one half the radials. The plates above 

 the first costals curve gradually upwards, and the two upper rows stand at 

 right angles to the truncated lower part of the calyx. Ventral disk low- 

 pyramidal, slightly grooved toward the arm bases -, the plates flat, covered 

 with numerous small pustules. The plates of the dorsal cup are grotesquely 

 ornamented with a variety of prominences and depressions ; some of them 

 elevated into sharp, very conspicuous, transversely rounded nodes, others 

 sharply pointed ; and from all of them somewhat irregular, subangular ridges 

 pass out to the margins of the plates, connecting with similar ridges from 

 adjoining plates. The plates of the rays have no nodes, and but few ridges 

 proceed upwards; those directed laterally form a well defined pentagon 

 around the basal concavity. In the upper part of the calyx the nodes cover 

 the greater part of the plates, and the ridges are merely indicated at their 

 outer margins. 



Basals small, restricted to the bottom part of the cavity. Eadials nearly 

 as large as the two costals together. First costals quadrangular, narrower 

 than the radials ; the second pentangular, supporting upon one side an axil- 



