104 
resting on tlie truncated ventral edge of tlic licptagonal l)asal, and placed 
between two radials, whilst there are one or more costals in each ray, 
supporting strong arms of a single series of plates. Now, dismissing from 
consideration the j^i'ohoscis, which they also describe in JEsiocrinus, it is 
manifest that this is, without exception, quite the structure of Thialocrinm . 
The basal plates are said by Miller and Gurley to be four hexagonal and one 
heptagonal, whilst those of Ehialocrinus are now described as pentagonal and 
hexagonal respectively ; at the same time it Avould l)e possible, without being 
absolutely incorrect, to describe these plates in the latter genus under similar 
terms — in this way — a glance at the ligure of JEsiocrimis llarei, M and G.^ 
will shoAV that the four basal i)lates are rendered hexagonal by having their 
dorsal edges angled to lit into the emarginate ventral edges of every two and 
alternately conjoined infra-basals. Similarly AAuth the dorsal edge of the 
heptagonal basal. As a matter of fact, on dissecting a Avorn example of 
JPhicducrinus Clarlcel, and separating the plates, I find that they also possess 
a tendency to a like outline, but Avhen united iti situ this is imperceptible. 
Under these circumstances therefore, it appears that there is little or no 
difierence in the construction of the calices in PJdalocrlnus and JEsiocrinus. 
It is satisfactory to find the vicAA’s of the late Dr. P. II. Carpenter, of 
the affinities of Phialocrinus so much in accord AA'ith those of Mr.P. A. Bather, 
who places the genus AA'ith Graidiiocrinus, Ceriocrinus, and Eursacriyins in a 
section of his family Decadocrinidoe, termed the Graphiocrinites. In the 
latter “ the radianal is lost, but .... the brachianal remains in the 
limits of the dorsal cuji.” It may be explained that Mr. Bather’s radianal is, 
as already pointed out, a radial “ that has assumed anal functions ” ; AAdiilst 
the brachianal is that plate termed in the present pages the anal. 
Noav a word as to the name Pentadia, Dana, lest any should contend 
for its adoption as the generic appellation of this group. I presume the giving 
a name to a single, ortAA'O or three Crinoid plates, is not sulRcient AAnrranty for 
its adoption in a generic sense. Such was the origin of Pentadied, but 
fortunately there is every reason to believe, as Avill be explained hereafter, 
that the plates of tAVO distinct genera correspond to the structure of these 
Penladia plates, and that in consequence it must be relegated without further 
discussion to the synonymic list. 
* Jouni. Cincinnati Soc. Nat. Hist., 1890, XIII, I’t. 1, t. 4., f. 1. 
^ Ann. Mag. Nat. Hist., 1890, \^. (6), pp. 383 and 383. 
^ American Jourri. Sci., 1843, IV., p. lo2. 
