91 
In some instances, the two pentagonal infra-basal plates arc grooved 
by sulci passing from the columnar facet to the middle of tlieir respective 
infra-basio-basal sutures. This, at first sight, gives rise to a decej)tive sub- 
division of the infra-basal cup into five, instead of three plates, and is at 
times very marked. Such a subdivision is shown in one of Prof, de Koniiick’s 
figures.^ Of the construction of the body on the ventral side above the radial 
plates little or nothing is known. 
Sir P. McCoy states that the jfiates seem in some cases to overlaj) 
each other. This, I think, only arises from a partial bevelling of the edges, 
which many of them appear to possess. 
Both McCoy and De Koninck have mentioned a partial ornamentation 
of the calyx plates. The former observes : “The surface is smooth, with the 
exception of a few irregular radiating plicce at the margin of some of the 
plates.” The latter Author’s description is similar, but along the edges 
of some of the plates he observed a few irregular concentric growth lines, 
instead of radiate markings. I have only met with two examples in which 
the calcareous test was preserved, all others having been in the form of casts. 
The two in question have smooth plates, quite devoid of ornament of any 
kind, but in every instance of an internal cast, or with decorticated plates, 
markings are present, and highly interesting and peculiar. 
It will bo remembered that Prof, de Koninck identified" Dana’s 
anomalous genus Fentadia with the plates of the so-called Cyathocrinus 
Konincld, Clarke, but an incidental remark of Ptatte’s carries equal weight, 
and is almost as near the truth. Speaking of the relation of the plates in 
question to Cyathocrinus, he says : “ But they might as well be separate 
plates of TrihracliiocriniisF'' Quite so! But, as a matter of fact, both 
Authors are correct, for I have no doubt that Dana’s larger plate, knoAvn as 
Pentadia corona, is one of the large radials of Phialocrinus Konincld, Avhilst 
the form of sculpture is common both to this and Trihracldocrinus Clarkei. 
Pirst, as to the appearance of this so-called ornament on internal casts. 
It is faintly exemplified in De Koninck’s figures^ of the present species, and 
more strongly so in our PI. XIII, Pigs. 2-4, both as regards the concentric lines, 
and two or three radiating ridges ; but in McCoy’s figures,® udiicli rej^resent 
calices with the test preserved, the plates are practically plain. 
*Fos 3. Pal. Nouv. -Galles clu Sud, 1877, Pt. .S, t. 6, f. 5d. 
'‘■Loc. cit., p. 165. 
^Proc. Linn. Soc. X. S. Wales for 1884 [1885], IX, Pt. 4, p. 1159. 
* Foss. Pal. Nouv.-Galles du Sud, 1877, Pt. 3, t. 6, f. 5,5 a-d. 
* Ann. Mag. Nat. Hist., 1847, XX, t. 12, f, 2 a and b. 
