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Diagnosis of Ptilocrinus. — Monocyelic or cryp- 
todicyelic. BB completely fused (except pérhaps in . 
young). Facet restricted to ?/; width of R. Arms unbran- 
ched, free and pinnulate from Br; onward, the proximal 
Br being fixed, though not rigidly, by the heavily plated 
tegmen. Br, united to R by articulation, to Bro by syzygy 
usually; Br, and Br, united by syzygy, after which syzygies 
are infrequent and irregular. Subvective grooves pass from 
Br; over tegmen. Stem cylindrical or nearly so, relatively 
long and slender, joint-faces radiately striate ; fresh colum- 
nals arising in proximal region [existence of a persistent 
proximale uncertain]; distal end expanded [probably 
to form an encrusting root]. | 
The genotype is : 
Ptilocrinus pinnatus A. H. Clark 1907 (loc. cit.) 
1588 fÎm., off Moresby Id., Queen Charlotte group, N. 
_ Pacific. 
Diagnosis. — À Ptilocrinus with height of BB circa 
four-fifths that of RR, and about equal to diameter ot 
cup at basi radial suture. Sides of basal cup continuous 
with column. RR [described by Clark as « elongate », 
but figured by him as wider than high] with very broad 
median ridge continuous into arms. Facet about two- 
thirds width of R, facing outwards slightly. Interbra- 
chials and interambulacrals [apparently] smooth. Teg- 
. men apparently of greater height than the cup. Brachials 
and pinnulars smooth and equable in outline. Columnars 
all smooth-sided. 
Some of the statements in this diagnosis are based 
on the enlarged photographs reproduced im P. Bartsch’s 
1908. — SCIENCES. 20 
