96 
in the calyx ; anal plate much less transverse than in tlic type species, 
acutely pointed at its dorsi-lateral angle ; second anal or basal plate of anal 
tube, small and quadrangular. Three arm-bearing costals large, their 
articular surfaces forming an isosceles triangle, with deeply excavated facets ; 
radio-costal sutures Avido and gaping. Disk plates small, polygonal, chiefly 
pentagonal and quadrangidar. Columnar facet small ; column unknoAvn. 
Sculpture in the form of pits and anastomosing, tubercular, vermicular 
grooves on the infra-basal and basal plates ; diA’aricating tubercular ridges 
on the radials ; cast plain. 
Ohs . — Trlhrachiocrinus cornigatiis is an excellent and AA^ell defined 
species, and may be at once distinguished from the two preceding Crinoids by 
the sculpture of the plates ; and, as regards shape, the nearly perfect 
symmetry of the calyx. I say nearly perfect, because there is tlic slightest 
possible tendency to bulge toAA^ards the posterior side, but hardly noticable 
unless closely looked for. 
The late Mr. T. Datte described the impressions of very small plates 
betAA^een the arm-plates, Avliich he believed to be those of the A'ault, AVachsmuth 
and Springer, on the other hand, remark — “ Me seriously doubt if these plates 
. . . . are any such thing as Auult-plates ; Ave belicA^e, if they are plates 
at all, that they formed a part of the disk, and as such Avere coA’ering pieces.” 
Mr. llatto AA^as unquestionably right in referring to the impressions in question 
as those of plates, but Messrs. vVachsmuth and Springer are probably correct 
in their interpretation. 
The sculpture is seldom Avell preserved, the ridges dividing the 
A'crmicular grooves becoming Avorn ; but Avhen in a perfect condition are 
tubercular, as described by Mr. Ilatte. A peculiarly marked pentagonal 
plate is represented in Tl. XIV, Dig. 7, probably a basal. The sculpture has 
the general appearance of that of the present species ; but the ridges in the 
cimtrc arc distinctly radiate, and the surrouiuling pits circular and separate. 
It may possibly be a slight A'ariation in the ornament of T. corrugatus, or 
even a distinct species. 
The A^ermiculate-tubercular sculpture of the calyx of T. corrugatus is 
reproduced in a great measure in that of J^iipacligcrinm magister, Miller and 
Gurley,^ from the Upper Coal Measures of Missouri. AVc are indebted to 
Mr. D. G. Engelhard t for the presentation of some fragmentary specimens 
from Jamberoo. IMr. Ilatte’s originals are in the Australian Museum. 
^ Jourii. Cinciunati Soc. Nat. Hist., 1890, XIII, No. 1, t. 1, f. 1 and 2. 
