248 Triassic Echinoderms of Bakony. 
showed that much might be learned by applying this method of research. The 
Bakony material is not always well adapted for the preparation of thin sections, 
but those sections that have been successful have proved most instructive. Not 
only have they afforded novel criteria for the determination of species, of special 
value in those cases where the outer forms are merged in apparently inextricable 
confusion, but they have manifested many curious structures. Hesse had already 
shown that the radioles from the Cassian beds were rather aberrant from the normal 
Cidarid type, and this is fully confirmed by the more elaborate studies here published. 
Some of the radioles of course do not really belong to the Cidaridae; but even in 
those cases where the name «Cidaris» seems less inappropriate, such as C. Haus- 
manni, C. parastadifera, and C. trigona, the structures revealed are highly specia- 
lised and peculiar. For adequate discussion of them the reader must be referred to 
the individual descriptions and plates (pp. 150, 173, 186, 189, 193, 197, 200, 203, 
211, 214, 218, 222, 231, 233; pls. XIV—XVIII). The nature of the material rendered 
the preparation of microphotographs out of the question in many cases, so that all 
these complicated structures have been reproduced as pencil drawings. This of 
course is a lengthy process, but the utmost pains have been taken by Mr. G. T. 
Gwnuam, and I have myself repeatedly checked his drawings with all possible care. 
We may now enquire what light the facts contained in this memoir shed on 
the Evolution of the groups concerned. Fossil invertebrates of Triassic age 
have always this peculiar interest, that they come between the Palaeozoic and 
Mesozoic forms of life, which have in so many groups of animals seemed to be 
constructed upon distinct plans. The former generation of palaeontologists, to whom 
the intervening Triassic fossils were not so well known, were so struck by the 
differences that they were accustomed to place the Palaeozoic and the later genera 
in distinct Orders; thus, among Echinoderma were established the Palaeocrinoidea 
and Neocrinoidea, and the Palechinoidea and Euechinoidea. So soon as the con- 
ception of one continuous process of evolution became part of the everyday thought 
of working palaeontologists, the fundamental error that underlay these conceptions 
was perceived. In the first paper that I wrote on Crinoidea (Feb. 1889, Quart. 
J. Geol. Soc. XLV, p. 617) I took the opportunity of criticising the classification 
then current, and had the pleasure of seeing it abandoned shortly afterwards by 
those who had themselves done so much to found and elaborate it — Messrs. 
WacusmutH & Sprincer and P. Hersert Carpenter. The division into Palechinoidea 
and Euechinoidea has had a longer life, for it was still used by K. von Zrrrev in 
the second edition of his «Grundziige der Palaontologie» (1903, pp. 203, 206); 
but it had already been definitely discarded by my colleague Dr. J. W. Grecory in 
the chapters that he wrote for my volume on «The Echinoderma» in LankesTERr’s 
«Treatise on Zoology» (1900). In breaking down these divisions, the Triassic Echi- 
noderms have played an important part, but, since these broader questions may 
be safely regarded as already settled, the bearing that this memoir has on them 
needs only slight mention. 
The Encrinidae are in themselves a natural bridge; for the Family, at least 
as I have defined it (op. cit. 1900, p. 181), includes the Carboniferous genera 
Stemmatocrinus and Erisocrinus, and the Triassic Encrinus. Details of classification 
may be open to criticism, but there can hardly be any hesitation in placing Encrinus 
