89 
In T. Clarkei, on the other hand, the triangular outline of the anal is 
lost, whilst the plate I have called the second anal assumes a comparatively 
large size, is in shape elongately-triangular, or somewhat lanceolate, and 
extends well downwards between the anal and riglit posterior radial, and lies 
horizontally against the truncated apex of tlie azygous plate. 
As regards the sculpture, the plates appear to Ije plain in T. Clarkei, 
radiatcly-carinate in T. ornatus, vermicular-rugose in T. corrugatus, and 
granular in T. gramdatus. 
As to the systematic position of Tribrachiocrinus, it is satisfactory to 
find that McCoy’s view, that the general disposition of the plates is most 
analogous to that of Foteriocrinus, is generally upheld by Messrs. Wachsmuth 
and Springer, who say, “ the radials enclose the azygous plate proper and an 
anal piece, as in most of the Fotcriocrinklce” On the other hand, Mr. P. A. 
Bather in his classification^ of the Inadunata-Pistulata entirely separates 
Tribrachioerhms from Poteriocrinus and its allies, by placing it in a separate 
Eamih^, the Decadocrinidm, associating the genus with Eupachijerimts, 
Cromgocrlnus, and Agassizocrinus, in the section Cromyocrinites. But, 
whilst acknoivledging the force of the retention of tlie “ three anal plates 
. . . . in the cup ” as a strong character welding these genera together, 
I prefer to retain the old classification until Mr. Bather has elaborated his in 
a more ample form. By Prof. K. Zittel, Tribrachiocrinus is erroneously 
ascribed to Austin. 
The genus, as regards its species, clearly dissolves itself into two Avell 
marked groups : — 
A. Calyx highly asymmetrical as to its form, Avith a protuberant 
posterior side — 
Tribrach yocr inns Clarkei, McCoy. 
,, ornatus, Eth. fil. 
B. Calyx more or less symmetrical as to its form, Avith the posterior 
side hardly at all protuberant — 
Tribrachiocrinus corrugatus, Ratte. 
„ granulatus, Eth. fd. 
Type—TribracMocrinus Clarkei, McCoy. 
Range — Permo-Carboniferous — New South "Wales and Tasmania. 
‘Ann. Mag. Nat. Hist., 1890, V (6), p. 383. 
