UINTACRINUS: ITS STRUCTUEE AND RELATIONS. 29 



basals, and abuts against them by their inner faces, instead of by their outer 

 or dorsal sides. It does not envelop or conceal the infrabasals, as the 

 proximal columnal does in pseudomonocyclic forms ; nor the basals and 

 radials, as the representative of the stem in the Comatulae usually does, — 

 although there is an exception to that in the case of certain living species 

 of Actino?iietra, and in many fossil Comatulce. On the o-tlier hand, the orien- 

 tation of the centrale is precisely as the stem should be ; i. e., interradial 

 when the infrabasals are present, and radial when they are not. And the 

 orientation is strongly against tlie third of the above suppositions. For the 

 gap left by the disappearance of the stem, and to be filled up by stereom, 

 would be the axial canal piercing the base of the calyx at the centre of the 

 basal or infrabasal ring. This would be radial in the latter case, and inter- 

 radial in the former. A supplemental plate developed to fill up this space 

 should have the same orientation ; but this is just the reverse of what is 

 exhibited by the centrale. It seems to me, therefore, that the argument 

 is decidedly in favor of the view that the centrale is a relic of the stem 

 of the Stalked Crinoids, — if not, indeed, of the pedunculate stage of 

 Uintacrinus itself. 



There is no doubt that the occurrence of these two forms of base in 

 this genus is a most extraordinary fact. Nothing like it has ever been 

 observed before among the Crinoids, to my knowledge. AVachsmuth and 

 Springer * held the presence or absence of infrabasals to be a good family 

 character, except in case of the Reteocrinidaj, in which dicyclic and mono- 

 cyclic genera — otherwise markedly similar — were included by us. It 

 was the difficulty presented by these genera that prevented us from attrib- 

 uting to this character a higher value and wider significance. Mr. Bather.f 

 on the other hand, considered the difference in tlie two forms of base as 

 sufficient to separate the Crinoidea Inadnnata into two sub-orders. He has 

 lately, in the chapters on the Echinoderma in Part III. of Ray Lankesters 

 Treatise on Zoology,^ of which he was kind enough to send me advance 

 proofs, elaborated a scheme of classification, embracing the whole of the 



* Monograph Criuoidea Canicrata, ]). 174. 



t Crinoidea of Gotland, 1893, p. 20. 



X This portion of the work embraces a treatise on the Cjstidea, Blastoidea, and Crinoidea. It contains 

 a full morphologic and systematic account of the three classes, and their subdivisions down to genera. It 

 brings into convenient form the results of all researches on both fossil and recent forms. Mr. Bather's con- 

 clusious will not all be accepted, but I wish to bear testimony to the great value of the work. Its compre- 

 hensiveness of treatment, lucidity of statement, and facility of illustration will render it of great use to 

 students of these groups. 



