SUMMARY. 
185 
Genus 28. — Plumaster, Wright (Vol. 11, p. 112), 
Body stellate, rays numerous, elongate, expanded in middle, provided on under 
side with a single row of marginal plates, transversely elongate, slightly arched, 
pectinated on one border, and displaying a single row of tubercles carrying long spines. 
Ambulacral furrow narrow and depressed. Radial ossicles at the angle of the rays very 
prominent and sculptured. Two rows of ambulacral pores. Genus found in the Liassic 
strata. One British Liassic species (Vol. II, p. 112). 
Genus 29. — Astropecten, Linck (Vol. II, p. 113). 
Body stellate, depressed, rays five, elongate. Margin of rays provided with two 
rows of marginal plates, those on under side bearing spine-like scales, which increase in 
size from within outwards, and terminate in long spines ; those on upper side covered 
with granules and often becoming spinous. Upper surface of body and rays (apart 
from the marginal plates) clothed with granules or plates, which are crowned with 
groups of minute spines. Ambulacral furrows more or less broad. Two rows of 
ambulacral pores. Range of genus from the Lias to existing period. Thirteen British 
Liassic and Oolitic species (Vol. II, pp. 113 — 129, 168). 
Order III.— OPHIUROIDEA, IFH^ld (Vol. I, p. 5; Vol. II, p. 131). 
Body {disc) discoidal, depressed, having long slender arms (ra?/s), destitute of an 
excavation for the viscera. Upper surface of disc supporting at base of arms ten large 
calcareous pieces {radial plates), sometimes close ' together, sometimes entirely naked, 
sometimes partly clothed with the general covering of the body. Under surface of disc 
bearing large smooth pieces {buccal plates) of different forms, generally single, and ten in 
number, sometimes doubled, and consisting of an inner larger and outer smaller portion. 
Under surface of disc also marked in each of the angular spaces between the arms {inter- 
brachial) by genital openings {Jissures), either two or four, or ten. Mouth {oral 
opening) always central, on the under side provided with a masticatory apparatus consisting 
of a cone of calcareous pieces, and always serving for the anal opening. Skeleton of many 
calcareous pieces variable as to number, size, and arrangement, and covered with an 
integument, either naked or bearing granules, scales, or spines. Rays simple or ramified, 
enclosed in four sets of jointed calcareous plates, one above, one below, and one on each 
side ; the lower set single, double, or quadrupal ; spines developed on the sides ; under 
surface not grooved and not pierced for tubular feet. Madreporiform tubercle on under 
