1002 ME. I". A. BATHEE OS UtNTACHlNUS. [DeC. 17, 



the stems \ Which view be ultimately accepted must depend on 

 the evidence of intermediate stages actually found fossil, stages 

 that shall bear the same relation to Uintacrinus as Thiolliericrinus 

 bears to Antedon. It is true that such links are still to seek ; but 

 the number of missing links is far fewer on this hypothesis than 

 on any other that has hitherto been advanced. 



4. SUMMAEY. 



This paper attempts a complete morphological description of 

 Uintacrinus socialis, and a comparison of it with U. ivesffalicMs. 

 The deficiencies of previous accounts are made good, and the errors 

 of them corrected : this is specially the case with regard to the 

 interbrachials, interpinnulars, brachials, pinnules, and joints. The 

 more accurate knowledge thus obtained enables a comparison \vith 

 other crinoids to be based on something more than external 

 appearances. It is thus shown that Umtacrinus cannot be related 

 either to the Camerata, e. g. to lihodocrinus as Jaekel has supposed, 

 or to the Ichthyocrinidae as maintained by Von Zittel, Neumayr, 

 and others. It must therefoi'e be related either to the Palaeozoic 

 Inadunata or to their Mesozoic descendants, the Canaliculata 

 ( — Articulata of Miiller). Among these, a process of comparison 

 and elimination leaves behind only the ascending evolutionary line 

 that contains Riicrimis, Dadocrinus, Pentacrimis, and A^nocrinus ; 

 and a simple inspection then enables us to fix on Dadocrinus as 

 the one among all known genera that is the most nearly related to 

 the ancestor of Uintacrinus. 



Whether this conclusion be right or wrong, I should like to 

 point out that it was not present to my mind when this investiga- 

 tion was begun, and that it has been arrived at solely by observation 

 of a large number of facts and by simple induction from those facts. 

 The circumstance that this conclusion differs from those of more 

 eminent writers arises partly from the revision and increase of 

 the facts concerning Uintacrinus itself, partly from the broader 

 principles that a more accurate knowledge of the Crinoidea now 

 enables us to apply. Knowledge cannot be too accurate or too 

 detailed. It is not till the details have been accumulated that we 

 can understand their meaning. 



^ Cf. D. C. Daaielssen, " Crinoida," Norske Nordhavs-Exped. xxi., Zoologi, 

 pp. 11-14 (1893) ; also Editorial on " Autotomy in Echinoderms," Natural 

 Science, vol. v. p. 4 (July 1894). 



