90 
Tribraciiiocrinus Clarkei, McCoy. 
PI. XIII, Pigs. 2-4. ; PI. XIV, Pig, 3 ; PI. XV, Pigs. G-8, aud ? 5 ; PI. XVII, Pigs. 2-4. 
Tribrachyocrimis Clarhei, McCoy, Ann. Mag. Xat. Hist., 1847, XX, p. 228, t. 12, f. 2. 
3j Clorkei, IMcCoy, Proc. E. Soc. V. D. Land, 1851, I, p. 315, t. 12, f. 2. 
33 Clorkei, l)c Koninck, Poss. Pal. Nouv.-Galles du Sud, 1877, Pt. 3, 
p. IGl, t. G, f. 5, 5 a-cl. 
53 Clarhei, Etheridge, fil.. Cat. Australian Poss., 1878, p. 41. 
Tr Ihrachiocrinus Clarhei, 'Wachsmuth and Springer, Eevision of the Palpeocriuoidea, 188G, 
Pt. HI (2), p. 251 (175). 
53 Tasinauicus, Johnston, Proc. E. Soc. Tas. for 188G [1887], p. 231. 
Sp. Char. — Calyx largo, deeply cup-sliaped, always produced asym- 
metrically towards the posterior side ; plates thick, with strongly bevelled 
edges ; greatest periphery at about one-third from the articular surfaces of 
the costals, or as near as possible along tbe basi-radial sutures ; above this 
point the calyx is usually depressed or somewhat flattened. Infra-basal 
jilates forming a shallow, asymmetrical, saucer-shaped cup. Ileptagonal 
basal very large. Radials bearing costals, strongly shield-sbaped, extended 
laterally along the articular margin into short angular processes. Azygous 
plate very large, always convex, and sometimes subangular i2i the middle 
line, according to the asymmetry of the calyx, its upper edge not extending 
to a point in line with the top ventral margin of the radials, but truncated 
and supporting the basal plate of the ventral ; anal plate pentagonal, large, 
its ventral margin on a line with the ventral margin of the radials ; second 
anal, or basal plate of tbe ventral tube, apparently quadrangular in shape, 
and much higher than broad. Costal plates large and transverse, with large 
articular facets. Columnar facet small ; column unknown. Test unsculp- 
tured externally, l)ut when decorticated^ the jdates present close concentric 
subimbricating ridges, wbich, towards the usually convex centres of the plates 
give place to undulating or festoon-shaped lines, resulting in a pentagonal or 
hexagonal star-shaped figure, according to the outline of the resjiective 
plates. 
Ohs. — I have included the asymmetrical form of the calyx as one 
of the specific characters from the fact that every specimen which has come 
under my notice is protruded towards the posterior side. One other species 
is similarly formed, but the remaining two are symmetrical in shape. 
' By far tlie much more common condition. 
