109 
well defined point, and directed perpendicularly towards 'the middle of each 
of the five sides. This arrangement presents an nnmistakeahle analogy to 
the fossil figured and described hy Dana under the name of Fentadia corona. 
Indeed, this fossil corresponds so well in form and size with the sub-radials 
of our Cyathocrinus, that I am led to hclieve it may he nothing more than 
one of these pieces. In that case, these suh-radials would he ornamented 
not only with the radiating costce that I have just mentioned, hut also with 
concentric granulated striae parallel to the margins.” De Koninck is, no 
douht, correct in describing such radiating folds and concentric granular 
ridges on the basal plates of P. Koninchi, for such are visilde in his figures, 
and more satisfactorily on one of our own (PI. XVI, Pig. 2). But, as regards 
the identity of Dana’s Fentadia plates wholly with the hasals of the present 
species, this, I think, can only he admitted in part, for it has already been 
shown that some of the plates of Trihrachiocrimis ClarJcei, when in a 
particular state of preservation, also display a similar arrangement of con- 
centric lines and radiating ridges. Such a reference was evidently conceived 
hy Prof. Dana himself^ when describing the several plates under the united 
name of Fentadia corona. 
The figure of P. corona‘s given hy Dana hears about six folds passing 
from the node-like centre to the middle of the plate margins, not to the 
angles. To the latter are other subsidiary ridges, rather than folds, thus 
dividing the surfaces of the plate into twelve triangular sj)aces. The object is 
further crossed concentrically hy a series of semi-imhricating lamina?, becoming 
coarser and more distant from one another towards the centre. It must he 
borne in mind that so perfect an example as figured l)y Dana is seldom seen, 
hut a glance at our PL XVI, Pig. 2, and the upper figure of De Koninck’s 
illustratioiP exhibit the points referred to sufficiently well to warrant tlie 
assumption that his Fentadia spatangus^, as it was originally termed, is 
identical with the hasals of P. Koninchi. At the same time, I must confess 
that, should the two Crinoids P. Koninchi and Trihrachiocrinus Clarhei he 
found together in a disintegrated form, it would require a critical study of 
the outlines of the plates to differentiate between the respective species in 
that condition. The reference of PI. XV, Pigs. C-8, and PI. XXII, Pigs. 
G-9, to the latter species is based on the fact that more perfect remains 
of T. Clarhei occur in company with them at the same locality. 
* Wilkes’ U.S. Explor. Expecl., 1849, X (Geology), Atlas, Expl. PI. 10, f. 10. 
® Loc. cit. t. 10, f. 10, 10a. 
2 Foss. Pal. Nouv.-Galles du Sud, 1877, Pt. 3, t. 6, f. 4. 
‘ American Jouru. Sci., 1847, IV., p. 152; Wilkes’ U.S. Explor. Exped., 1849, X (Geology), Atlas, t 10 
f. 10, 10a. 
