298 FIELD CoLUMBIAN Museum — Geo ocy, VoL. II. 
by the beveled edges of the plates. No radial ridges are observed. 
The natural cast is turbinate, pointed below and truncated above, 
with prominent arm bases. Arms, judging from the arm bases, two to 
each ray. 
Basals three, equal in size, forming a shallow cup with an hexag- 
onal outline. Radials five, height and width about equal, the two 
anterior laterals heptagonal, the others hexagonal, in contact except 
at the posterior side where they are separated by the first anal plate. 
First costals quadrangular, height and width about equal, much 
smaller than the radials. Second costals about the size of the first, 
wider than high, pentangular, axillary, supporting the distichals upon 
their sloping edges. Distichals comparatively large, two or more to 
each ray. The first interbrachial plate is imtermediate in) size 
between the radials and the first costals; it is nine-sided and occupies 
the space from the sloping superior edges of the radials to the inferior 
edges of the distichals; it supports a narrow plate upon its upper edge. 
No interdistichals are observed. The anal interradius is considerably 
wider than the interbrachial areas. The first anal plate is heptagonal, 
pa on the basals between the posterior lateral radials. It is 
Uj r three plates in the second row and by five in the two 
rows. 
in the arrangement and relative size of the plates this species 
closely resembles H. (Pionocrinus) farctus Angelin * (See Fig. 10), but. 
that is a very small species and the plates are moderately convex and 
without sculpturing. The distinguishing characters between this 
species and H. jarringtont are discussed under that species. 
The type specimen ( Mus. No. P 9628 ) consists of a somewhat 
weathered natural cast with a portion of the accompanying natural 
mold. The mold comprises the basal cup in good condition, three 
radials and the first anal plate practically complete and the lower half 
of the other two radials; in two of the rays the costals and one of the . 
distichals are preserved with the enclosed interbrachial area. The 
impression from this mold gives the general form of the exterior 
of the dorsal cup and the ornamentation of the plates. The form 
of more than half of the plates can be traced on the natural cast, so 
that the characters of the species can be ascertained. The pits on the 
basal and radial plates, shown in Pl. LXXXVII, Figs. 8 and 9g, are 
caused by protuberances in the natural mold. These protuberances 
appear to be carbonate of lime deposited after the original crinoid 
had been dissolved out, and probably have no connection with the 
ornamentation of the plates. 
* Tconographia Crinoideorum, p. 5, Pl. XVI, Fig. 23. 
