82 Reviews—R. Etheridge, jun.—Fossils of N. S. Wales. 
with radiating lines of very peculiar wart-like tubercles, concave at 
their apices.” It seems to us very probable that these tubercles 
once bore spines like those of Hystricrinus, which is a Devonian 
form closely allied to Platycrinus, occurring in North America. 
The remarkable genus Tribrachiocrinus is described afresh from 
the evidence of four species, of which two—T. ornatus and T. 
granulatus—are new. ‘The dorsal cup in this genus is composed 
of three circlets of plates, viz., infrabasals, which are three, owing 
to the fusion of two pair; five basals, of large size and irregular 
shape ; and five radials. In the posterior interradius are three plates, 
namely, the radianal, the anal x, and a plate between « and the right 
posterior radial resting on the radianal. Thus far the crinoid closely 
resembles Eupachycrinus and Cromyocrinus from the Carboniferous 
of America and Europe; but, turning to the arms, we find great 
peculiarities. In the anterior and in the left and right posterior 
rays, the radial has a wide articular facet (as in the genera just 
mentioned), on which works a wide brachial, usually narrowing 
above; this appears to have been followed in T. ornatus, which 
alone presents traces of arm-branches, by three more primary 
brachials the last of which supports ‘two arm-branches; whether 
these latter branched again is uncertain. The left and right anterior 
radials, however, had no wide articular facet, but seem to have 
become fused with one or more of the primary brachials, and to 
have borne no regular arms. This view, to which Mr. Htheridge 
gives his support, resembles that of the earlier writers in that it 
ascribes only three main arms to the genus, and differs from 
that of Wachsmuth and Springer (which is misrepresented by Mr. 
Etheridge). To such a view there is no a priori objection, for 
much the same state of things is found in Berocrinus Ungerni; at 
the same time it is hard to reconcile it with the figure of T. ornatus 
(plate xix.), which appears to show not six but at least ten series 
of distichals. 
With reference to the tegminal plates of T. corrugatus, which 
Ratte described as vault-plates, but which Wachsmuth and Springer 
believed to be part of the disk, both parties were correct; for there is 
no difference between vault and disk. 
As to the systematic position of Tribrachiocrinus, it may be pointed 
out that the Poteriocrinide of Wachsmuth and Springer included 
genera which, though they had arrived at a similar stage of evolution 
as regarded the anal area, seemed nevertheless to have sprung from 
two distinct stocks, one characterized by repeatedly dichotomous 
arms, as in Poteriocrinus, the other with arms in two main branches 
only, as in Decadocrinus. 'To these latter genera the name Decado- 
crinidz has been applied, and among them there is at present reason 
to suppose that we must reckon Hupachycrinus, Cromyocrinus and 
Agassizocrinus, three forms that agree in the possession of a globose 
dorsal cup, large basals, a large radianal and a wide articular facet 
to the radial, characters, which, as we have seen, are also con- 
spicuous in the cup of Tribrachiocrinus but not in that of Poterio- 
crinus. We regret therefore that Mr. Etheridge should prefer to 
retain the two latter genera in close association. 
