1879.] NATURAL SCIENCES OF PHILADELPHIA. 317 



*1860. Arachnocr. pisiformis Roemer. (Posteriocr. piriformis), Sil. Fauna of 

 West Tenn., p. 54, pi. 4, figs. 7 a-d ; Meek & Worthen, Arachnocr. pisi- 

 formis. Geol. Rep. III., vol. ii. p. 177. Upper Silur. Tenn. 



The arms are unknown in this species. 



10. VASOCRINUS Lyon. 

 (Rectified by W. & Spr.) 

 1857. Geol. Surv. Kentucky, vol. 3, p. 485. 



Hall Advance Sheets Pal. New York, Vol. V., Part II., p. 6, 

 containing a list of the Devonian fossils occurring at the falls of 

 the Ohio placed both species of Lyon's Vasocrinus under Cya- 

 thocrinus, in which he was apparently justified ; for Lyon in de- 

 scribing the genus failed to point out any characters by which it 

 might be distinguished from Cyathocrinus, except perhaps the 

 peculiar form of the body. In his generic description Lyon men- 

 tions the presence of only a single anal plate, but at the same time 

 describes his second species with two anals. On examining the 

 original specimens, both of V. valens and V. sculptus, in the col- 

 lection of Dr. Knapp, we arrived at the conclusion that Lyon was 

 correct in separating these species from Cyathocrinus, and further- 

 more, that they are intimately related to certain other species 



umn. Basals large, larger tban the radials, and partly included within the 

 concavity. Radials of unequal size the posterior ones smaller semilunu- 

 late ; articulating facet strongly excavated, facing outward and almost cir- 

 cular in outline. Brachials very heavy, their number varying in the rays. 

 In the original specimen the left posterior ray has fourteen brachials ; the 

 right posterior evidently recuperated and hence perhaps not showing its 

 normal condition has eight ; the lateral rays twelve to fourteen, and the 

 anterior ray fourteen. The first and only bifurcation visible in the speci- 

 men takes place on the second, third, or fourth plate. Arms erect, being 

 otherwise built upon the same plan as in A. extensus. Arm joints as heavy 

 as the brachials, cylindrical, much wider than high, with parallel sutures, 

 and without pinnulte. All these plates appear as if constricted in the mid- 

 dle, on account of the thickening of the plates toward the sutures. Anal 

 arrangement not clearly disclosed in the specimen, but there appears to be 

 a rather large lateral opening directly above the posterior basal and be- 

 tween two adjoining radials. We can observe no special aual plate, and if 

 it were present it was evidently small, and perhaps formed a part of the ven- 

 tral tube, which toward the dome is supported by an elongate lozenge- 

 shaped oral plate. Four additional oral plates of a similar form cover the 

 ventral side. Apical dome plates, and the covering of the ambulacral 

 furrow, not preserved. Hamilton Group. Devonian. Near Charleston, 

 Indiana. 



