420 Mr. P. H. Carpenter on certain Points in 
meaning, and can only hope for a further explanation of it 
in his forthcoming monograph. 
An extensive series of observations which have been made 
conjointly by Mr. R. Etheridge, Jun., and myself *, enables us 
to give a general confirmation to the results of Wachsmuth 
and Hambach. We cannot with certainty detect more than 
one subambulacral plate in any species of Granatocrinus, 
either British or American; but we cannot agree with Wachs- 
muth in considering its longitudinal canal as corresponding 
to the dorsal canal of a Crinoid arm, which lodged the axial 
cord; for we believe it to have contained the water-vessel. 
We think, however, that he is correct in describing two sub- 
ambulacral pieces in Pentremites; but we are not quite clear 
as to whether both of these were perforated, or only one, and. 
if so, which of them. It is a matter of no little difficulty to 
attempt to solve problems of this kind on material which is so 
highly mineralized as most of these Blastoid calices are; and 
it is therefore satisfactory to find that the observations of 
three independent sets of workers are fairly in accordance 
with one another. 
Besides the lancet-piece and the poral pieces, there is, ac- 
cording to Dr. Hambach, another element which enters into 
the composition of the ambulacra of the Blastoids, viz. “the 
zigzag plicated integument. ‘This may be regarded as a 
band which is transversely plicated and covers the whole 
ambulaeral field; it was probably of an elastic texture during 
the litetime of the animal. It commences at the apex of the 
ambulacral field, running in a zigzag from the lateral 
margin to the median line, so that the poral openings are 
always placed between two returning folds, which are flattened 
here to form a sort of articulating surface for the pinnule. 
It ascends in this manner, covering half of the ambulacral 
field, to the summit of the calyx, where it surrounds in a very 
acute angle two of the ovarian openings, and descends in a 
like manner on the following ambulacral field.” 
Two figures are given by Dr. Hambach in illustration of 
the novel statement which I have quoted. One of them 
represents a portion of an ambulacral field considerably mag- 
nified; and in some points it is more correct than any which 
has yet been published. Thus the pinnule-sockets are 
shown to be distinct from the marginal pores, as was long ago 
described, though not figured, by Billings Tt, whose observa- 
* “Remarks upon the Structure and Classification of the Blastoidea,” 
‘Nature,’ vol. xxiv. p. 497, and Geol. Mag. October, 1881, p. 464. 
+ ‘Canadian Naturalist,’ 1870, p. 184. 
