1000 MR. F, A. BATHER ON TJINTACRINUS. [DeC. 17, 



separated by small but well-defined iiiterbracbials, while a few 

 interdistichals are also present ; interbracbials also occur in Apio- 

 crinus roissyanus and A. elegans. In both these forms, however, 

 the plates of the cup are too thick, and the arms too much 

 branched, for us to infer any direct affinity with Uintacriniis. I 

 refer to these facts merely to show the possibility of a development 

 of interbracbials and interdistichals among the genera of the gi'oup. 

 Similarly the Pentacrinidae, notably Extracrinus, may develop 

 interbracbials ; and in E. lepidotus, at any rate, the proximal 

 pinnules seem to have been laterally united, forming thin scaly 

 plates. Moreover the whole arm-structure of Uintacriniis is 

 singularly like that of the Pentacrinidse. But we must look for a 

 form not so highly modified, and one in which the arrangement of 

 syzygies and pinnules does not conflict with the law of their 

 arrangement in Uintacrinvs. Thus, by a gradual process of elimi- 

 nation, we are forced back upon Dadocrinus, and here indeed 

 appears to be the object of our search. 



The genus Dadocrinus, based by H. von Meyer on Encrinns 

 r/racilis, von Bucb, which has been investigated by Beyrich, 

 Kunisch, Giirich, Wachsmuth and Springer, and above all by A, 

 von Koenen \ is admitted to be an ally of Ensocrinns, Stemmato- 

 crinus, and Encrinus, and to be intermediate between them and the 

 Pentacrinida; and Apiocrinidae. "Whether or no it be the actual 

 ancestor of the latter families, it at least comes as near as possible 

 to what that ancestor must have been. It is pseudo-monocyclic, 

 has 2 primibrachs, pinnulate arms bifurcating once, with a separate 

 axial canal ; its primibrachs are united by a number of small 

 interbracbials which pass up into a thin-plated flexible tegmen. 

 The arrangement of pinnules and syzygies in the proximal region 

 of the arms is governed by the same law, and subject to the same 

 regular exceptions, as in Uiniacrinus (fig. 13)^. The proximal 

 pinnules are larger than the others, and have flat backs and square 

 sides, thus resembling the coadunate pinnules of Extracrinus. 

 Now in all these essential points of structm-e, Dadocrinus gracilis 

 agrees precisely with Uintacriniis. All that we have to suppose is 

 a gradual exaggeration of these features and the loss of the stem. 

 The former is a natural supposition, since, as has just been shown, 



' "Beitrag zur Kenntniss der CriBoiden des Muschelkalks," Abh. Ges. 

 Wiss. Gottingen, xxxiv. Phys. Kl. i. pp. 1-44, pi. i. (1887), and " Ueber dieEnt- 

 wicklung von Dadocrimts gracilis, v. Buch, uud Holocrimts wagiieri, Ben., und 

 ihre Verwandtsehaft mit anderen Crinoiden," Nachricliten Ges. Wiss. Gottin- 

 gen, Math. -phys. Kl. Jahrg. 1895, pp. 283-293 (pages 292, 293 being wrongly 

 imposed), 14th Dec, 1895. In these papers references to the rest of the 

 literature will be found. 



- Von Koenen [op. cit. 1895) describes the pinnules as borne on the outer 

 side of IlBr^, on the inner side of IIBrj, and thence regularly on each secundi- 

 braoh, on the outer and inner sides alternately. The syzygies that are to be 

 inferred from this arrangement agree with the plan of Vintacriiiun. But I have 

 found yet other arrangements, which make the resemblance still more strikirg. 

 A slab in the British Museum (E 6070) enables one to trace the arrangement 

 in several arms. The commonest type has syzygies between seeundibrachs 1 & 2, 

 3 & 4, 6 & 7 ; pinnules are borne by the epizygals and by IIBr^, first on the 



