ORDER I BLASTOIDEA—REGULARES ROG 
five, piercing the apices of the deltoids. Posterior spiracle larger, including 
the anus. Summit closed by minute pieces which rarely exhibit any definite 
arrangement. Sub-Carboniferous ; England and North America. 
Heteroblastus, E. and C. Resembling the preceding in form and proportion 
of its component parts. The proximal ends of the deltoids produced in short 
spine-like processes, at the base of which minute lateral openings, one to each 
deltoid, are visible. These openings lead into gutter-like channels excavated 
in the substance of the plates for the reception of the proximal ends of the 
two hydrospire- canals. Radial sinuses wide, their edges sloping gently 
downwards to the slightly petaloid ambulacra. Carboniferous Limestone ; 
England. 
Family 5. Codasteridae. Etheridge and Carpenter. 
Base usually well developed, and sometimes very long. Ambulacra without 
marginal pores. Hydrospire-slits either wholly exposed, piercing the calyx plates 
along the sides of the radial sinuses, or restricted portions of them remain open as 
spiracles, while the remaining parts are concealed by the ambulacra. Devonian and 
Lower Sub-Carboniferous. 
Codaster, M‘Coy (Codonaster, Roemer), (Fig. 323). Calyx inverted, conical, 
or pyramidal. Upper face broad, truncate, or gently convex; section, as a 
rule, distinctly pentagonal. Basals forming a conical or triangular cup, 

Fic. 323. 
NG. 32 
Codaster acutus, M‘Coy. Carboniferous Lime- sec Sees 
stone; Derbyshire. A, Side-view of calyx. Orophocrinus stelliformis, O. and 8. sp. A, Calyx 
B, Base. C, Ventral aspect, enlarged (after and base of the natural size. B, Ventral surface en- 
Roemer). larged (after Meek and Worthen). 
usually deep. Radials large, their limbs bent inward horizontally, to assist 
in forming the truncated upper face of the calyx, and never deeply excavated 
by the sinuses. Deltoids wholly confined to the upper face, as are also the 
ambulacra. The latter are petaloid, or narrow and linear ; lancet-plate, as a 
rule, deeply excavated for the side-plates. Spiracles absent, hydrospires 
pendent, arranged in eight groups, two. in each of the four regular interrays, 
but wanting in the anal one. The tubes open externally by a variable number 
of elongated slits, which are separated by intervening ridges ; one or more of 
them may be partially concealed by the overlapping side-plates. Anus large, 
ovate, or rhombic, and piercing the posterior deltoid. Ornament consisting 
of fine lines arranged parallel to the margins of the plates. Silurian to Sub- 
Carboniferous ; Europe and North America. 
Phaenoschisma, E. and C. Calyx resembling that of Codaster in general 
form, but with ten groups of hydrospires instead of eight. Radials bear each 
three more or less distinct folds diverging from the lip; sinuses wide and 
