BLASTOIDEA REGULARES 



197 



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. Kesembling the preceding in form and proportion 

 of its component parts. The proximal ends of the deltoids produced in short 

 spine-like processes, sit tin- bas- 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 

 ni'injinal pores. JIt/'/rx/>ire-slits either whollij exposed, piercing the calyx plates 

 tifiniff 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, 



Codastn- unit,'*, M'Coy. Carboniferous Lime- 

 st<m.-; Derbyshire. A, Side-view of calyx. 

 B, Base. C, Ventral aspect, enlarged (after 



I-' 1 1 '-^9d 



Orophocrinus stelliformis, O. and 8. sp. A, Calyx 

 and base of the natural size. B, Ventral surface en- 

 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 



