168 PROCEEDINGS OP THE ACADEMY OP [1886. 



forming a shallow inverted cup, decagonal at the outer side, 

 Basals trigonal, ver}'' minute, irregular in size, the two anterior 

 ones smaller than the others. Radials large ; broadly truncate 

 below ; subquadrangular in outline but hexagonal ; the three 

 lower faces scarcely as wide as the lateral ones, and narrower by 

 one-half than the upper side. Brachials 1X5; four of them tri- 

 angular, giving off two arms each ; the anterior one quadrangular, 

 with only one primary arm. The arms bifurcate on the fifth 

 plate, and again on the tenth to fifteenth ; the higher divisions 

 are not known." In this species, exceptionall}'^, the inner arms 

 branch again. 



Azygous plate elongate, resting upon the underbasals ; the 

 right lateral face, which is slightly convex, abutting against the 

 right posterior radial, its upper side supporting the anal plate ; 

 leaning with its left lateral side against the other radial, and with 

 its lower sloping side against the adjoining basal. 



Geological Position.! etc. Keokuk limestone. White's Creek 

 Springs, near Nashville, Tenn. 



CCELIOCSINUS White, Rev. I, p. 131. 

 Syn. Sphreronites Phill., Palseoz. Foss. Cornwall, p. 135. 



We have heretofore made Coeliocrinus a subgenus of Hydreio- 

 nocrinus, owing to slight variations in the form and construction 

 of the ventral sac, which we thought to be the only distinctive 

 character. Beautiful specimens, however, which we obtained since 

 in Kentuck}^, show that the two forms differ in their mode of ar- 

 ticulation in a similar manner as WooclociHnus and Zeact'inufi, 

 Scytalocrinus and Eupachycrinus, which we ranked as full genera. 

 In Coeliocrinus the calyx is conical, in Hydreionoci'inus depressed 

 saucer-shaped. 



Coeliocrinus is found also in Europe. Phillips, in his work on 

 the Palseoz. Foss. of Cornwall, gives on PI. 59 a good figure of 

 what we take to be the balloon-shaped ventral sac of this genus. 

 His figure was copied from the Geol. Trans, (new ser.), vol. iii, 

 PI. 20, which had been published with a note by Mr. Broderip, 

 " calling attention to some analogy between this fossil and 

 Chelyosoma macleayanum, a species of tunicate Mollusca, which 

 has a few coriaceous plates on the upper surface ont}^" Phillips, 

 and apparently Austin, took it to be allied to Echinosphe rites of 

 Wahlenberg, and called it provisionally Sphseronites tessellafuSj 

 which we propose to change into Coeliocrinus tessellatus. 



