318 PROCEEDINGS OF THE ACADEMY OF [1879. 



which have been referred to various genera, and always with diffi- 

 culty. 



In reconstructing the genus, we prefer to make Vasocrinus Ly- 

 oni (Cyathocrinus Lyoni Hall), from Crawfordsville, the type, 

 because it is found more perfectly preserved in the arm portion ; 

 but we scarcely doubt, to judge from the brachials, as far as they 

 are preserved, that the arms in the Devonian species were con- 

 structed in a like manner. 



Revised Generic Diagnosis. Calyx shaped like a low vase ; 

 plates thin. Underbasals five, rather small, forming a regular 

 pentagon. Basals large, almost as high as wide, general^ de- 

 pressed toward their angles, four pentagonal or hexagonal, the 

 fifth with an additional side. Radial s always wider than high, 

 the upper portion strongly inflected toward the dome. Articulat- 

 ing facet, concave occupying about one-third of the plates, almost 

 circular, deeply notched for the ambulacral groove. Brachials 

 resembling the arm plates, but slightly wider. In Vasocr. Lyoni, 

 the only species in which their number is perfectly known, there 

 are two by five ( V. valens had at least as many), with two arms 

 to the ray. 



Arms long, moderately heavy, tapering gradually to the tips. 

 They are simple throughout, so far as observed, but in place of 

 branching they throw off armlets alternately from each side, and 

 these branch once or twice, as in Botryocrinus and Barycrinas, 

 though they are less robust. 



Anal area wide; anal plates generally two, rarely one, arranged 

 as in Barycrinus. There is one large plate situated between two 

 radials, and a smaller one placed obliquely toward the right side 

 of the specimen, and between two basals, the right posterior radial 

 and the larger anal. The ventral sac, as observed in V. Lyoni, 

 extends to more than half the length of the arms. It is rather 

 heav}', with a series of large quandrangular plates at the base, 1 

 the lower ones as wide, but much higher than the radials. All 

 the other plates of the sac are much smaller, decreasing in size 

 upward. Construction of the vault unknown. 



1 These plates, which are much heavier and larger than any other plates 

 of the tube, in their longitudinal arrangement and rounded exterior, 

 strongly resemble an arm, and were taken by Lyon and Casseday, who de- 

 scribed this species as Cyathocr. hexadactylus, for arm plates of a sixth 

 ray, and the large anal plate upon which they rest, for a radial. 



