Rofe—Actinocrinus, &c. 245 
II. Notrs on some EcHINODERMATA FROM THE MOouNTAIN- 
LIMESTONE, ETC. 
By Joun Rors, Esq., F.G.S. 
[Plate VIII. ] 
1. Actinocrinus. 
EVER years since, when collecting Mountain-limestone fossils 
on the borders of Lancashire and Yorkshire, I found some spe- 
cimens of Actinocrinus which appeared to have internal channels 
from the base of the arms towards the summit of the dome. Not 
having seen such channels noticed by any author, I showed some of 
the specimens to Mr. Salter, then of the Geological Survey, who 
suggested that they probably might be analogues of the aquiferous 
channels found in recent Echinoderms; and he advised me to follow 
up the subject, and ascertain if such passages were to be found in 
other Crinoidea occurring in these rocks. His advice has been fol- 
lowed, and a large collection of specimens, some in good preserva- 
tion and others weathered, has been made, which I have had the 
advantage of collating with a series from the same district collected 
by Mr. James Parker of the Manchester Museum; and upon exami- 
nation they give the following results, some of which, though pro- 
bably of no great importance in themselves, may serve to illustrate 
some doubtful points in the organization of this confessedly obscure 
Order of the Animal Kingdom. 
It is unnecessary here to give in detail the construction of the 
arms of the Crinozdea, as that has been done so satisfactorily by 
Messrs. Austin, M. de Koninck, and others; but, as I shall have 
hereafter to point out an exception, it may be shortly stated that 
they describe these arms as not being truly cylindrical, but as formed 
like a cylinder, or branching cylinders, having a deep longitudinal 
groove along the upper side, with a row of tentacles on each of its 
margins, forming an open channel throughout the whole length, 
until the arms join the body; but at this point, it will be seen from 
what follows, this channel is divided into two passages, an upper and 
a lower; the former passing up within the dome to the apex, where 
the passages from the five arms meet, the latter going direct into 
the visceral cavity. 
The species in which these passages were first observed by me is 
Amphoracrinus* rugosus. In this, and in all the species of this 
genus hitherto examined, the plates forming the dome are extremely 
thick ; and the upper passages above named are, for at least two- 
thirds of their length, in the snbstance of these plates; but in 
Actinocrinus the plates are thinner, and are arched over the pas- | 
sages. In the angle between two of these passages, on the anal 
side, the proboscis is placed. In Aetinocrinus this is close to the 
junction; but in Amphoracrinus it is more or less removed from the 
angle. Plate VIII. fig. 1, is a horizontal section of a specimen of 
* To avoid repetition and confusion, the genus Actinocrinus is, in this paper, 
divided into its sub-genera Actinocrinus and Amphoracrinus. 
