1070 NOTES ON AUSTRALIAN FOSSILS, 



This genus being hitherto entirely Australian, it will be suitable 

 to complete the description that I have given of the second 

 species known, by stating the opinion of Messrs. Wachsmuth and 

 Springer, (whose "Revision of the Palreocrinoidea," has justreached 

 its end), and the true place which, according to these gentlemen, the 

 genus considered ought to occupy in the order Palseocrinoidea. 



If we consider the calyx of a crinoid, we find that the base, to 

 which the stem is attached, is composed of a certain number of 

 plates. Let us take, for instance, Cyathocrinus, and Tribrachiocrinus, 

 both represented in our Carboniferous. In Cyathocrinus the base 

 is formed of five plates, and in Tribrachiocrinus of three plates, 

 but in both cases the figure is a pentagon. In some genera the 

 figure is an hexagon, though the former is the more frequent. The 

 number of divisions, although most frequently five or three, is 

 sometimes four or another number. 



From these considerations the late Prof. Angelin divided the 

 Silurian Crinoids of Sweden into four sections : Trimera, Tetramera, 

 Pentamera, and Polymera. But the progress in the study of fossil 

 crinoids, due principally to the authors of the ' Revision,' and to 

 Dr. P. Herbert Carpenter, has led to a classification upon more 

 natural principles. The last-named author in a paper on the ' Oral 

 and Apical systems of the Echinoderms/ " considers the basals of 

 recent crinoids to be homologous to the genital plates, and the 

 radials to the ocular plates of the Echini, and he traces the 

 homology to the Palseocrinoidea, in respect to which, however, he 

 advances the opinion that the first ring of plates resting upon the 

 upper stem segment, which have heretofore been nominated basals 

 are in many types not basals at all. He regards the set of plates 

 which lie next below the radials as the true basals, no matter 

 whether they rest directly upon the stem, as in Platycrinus, or are 

 separated from it by another ring of plates, as in Cyathocrinus ; 

 so that the sub-radials of most American authors, or parabasals, 

 as they are generally termed in Europe, are basals according to his 

 view. The lowest or proximal ring of plates, in types having 

 sub-radials, he calls underbasals, and these he believes to be 



