192 THE VOYAGE OF H.M.S. CHALLENGER. 
which they had been raised by Forbes, they had been, and were subsequently, still further 
degraded. For d’Orbigny’ took an entirely different view of the characters of the 
various types of the Pelmatozoa from those held by some of his predecessors ; and he not 
only threw the Cystids and Blastoids back among the Crinoids, but he considered these 
two groups merely as families. He divided the order Crinoidea into twelve families, 
among which are the Comatulidze, Pentremitidee, Cystidee, and lastly the Pentacrinide ; 
and Pictet” subsequently reduced this number to nine, but without making any change 
in the four above mentioned. 
Dujardin and Hupé” also adopted this singular arrangement, according to which the 
differences between a Pentacrinus and a Pentrenutes, Echinospherites or Actinocrinus, 
are of no greater systematic value than those between Pentacrinus and Comatula. In 
this country, however, thanks mainly to the teaching of Prof. Huxley,* Crinoids, Cystids, 
and Blastoids have always been regarded as independent but equivalent divisions, 
formerly orders, but now classes of the Echinodermata. To these Huxley’ has since 
added another, as to the necessity for which there has been a considerable difference of 
opinion, viz., the Edriasterida. 
This group, which includes the curious sessile forms dAgelacrinus, Edrioaster, and 
their allies, has been generally placed among the Cystids ; but it has been re-established 
quite lately under the name of Agelacrinoidea by 8. A. Miller, in ignorance of Prof. 
Huxley’s classification of fifteen years ago. 
I am inclined to think myself that if these forms be anything more than the 
isolated disks of Palaeocrinoids, as was thought possible by Sir Wyville Thomson (ante, 
p. 85), their proper place is among the Cystids. 
Two other new orders (i.e., classes) of the class (¢.e., subkingdom) Echinodermata have 
recently been proposed by 8. A. Miller.” These are the Lichenocrmoidea and the 
Myelodactyloidea. But I cannot regard them as of equal value with the Crinoids, Cystids, 
and Blastoids. Our knowledge of the structure of Iichenocrinus is of the most limited 
character ; and it is therefore totally insufficient for the basis of a class definition. The 
same may be said of Cyclocystoides, which together with the so-called Myelodactylus is 
placed by Miller in a new order that he proposes to call Myelodactyloidea. Whatever 
be the nature of Cyclocystoides, there can, I think, be little doubt that Salter, 
Charlesworth, and more recently Nicholson and Etheridge’ were right in regarding the 
1 Cours élémentaire de Paléontologie et de Géologie stratigraphique, Paris, 1852, t. ii. fase. i. p. 134. 
2 Traite de Paléontologie, t. iv. p. 282. 
3 Histoire Naturelle des Zoophytes, Echinodermes, Paris, 1862, yp. 55-58, 
4 Lectures on General Natural History, Medical Times and Gazette, November 1856, p. 463. 
5 An Introduction to the Classification of Animals, London, 1869, p. 130, 
6 Description of three New Orders and four New Families, in the class Echinodermata, and eight New Species 
from the Silurian and Devonian Formations, Jowrn. Cineinn. Soc. Nat. Hist., vol. v. pp. 221-223. 
7 A Monograph of the Silurian Fossils of the Girvan District in Ayrshire, Edinburgh, 1880, pp. 330-334. 
