168 



ECHINODEEMATA— PELMATOZOA 



PHYLUM IV 



Family 1. Oodasteridae Etheridge and Carpenter. 



Base usually well developed, and sometimes very long. Amhulacra without 

 marginal pores. Hydrospire-folds Coming to the surface of the radial sinus. 

 Hydrospire-slits either wholly exposed, piercing the calyx plates along the sides of 

 the radial sinuses, or restrided portions of them remain open as spiracles, white 

 the remaining parts are concealed hy the amhulacra. Devonian and Lower 

 Carboniferous. 



Codaster M'Coy (Codonaster Koemer; Heteroschisma WsLchsm.) (Fig. 260). 

 Calyx inverted, conical or pyramidal. Upper face broad, truncate or gently 

 convex ; section, as a rule, distinctly pentagonal. Basais forming a conical or 

 triangulär cup, usually deep. Kadials large, their limbs bent inward horizon- 

 tally, 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 amhulacra. The latter are petaloid, or narrow and linear ; 

 lancet-plate, as a rule, deeply excavated for the side-plates. Spiracles absent, 



Fig. 2Ü0. 



Codaster acutus M'Coy. Lower Carbonifer- 

 ous ; Derbyshire. A, Side-view of calyx. B, 

 Base. C, Ventral aspect, enlarged (after 

 Roemer). 



Fig. 261. 



Oropliocrinus stelliformis (O. and S.). Lower 

 Carboniferous ; Burlington, Iowa. A, Calyx and 

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

 larged (after Meek and Worthen). 



hydrospires pendent, arranged in eight groups, two in each of the four 

 regulär 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 Lower Carboniferous; Europe and North America. 



Fhaenoschisma E. and C. (Fig. 254, B). Calyx resembling that of Codaster 

 in general form, but with ten groups of hydrospires instead of eight. Radiais 

 bear each three more or less distinct folds diverging from the lip; sinuses 

 wide and deep, generally with steep sides. Deltoids small, confined to the 

 truncated upper face of the calyx. Lancet-plates in all but one species 

 (P. caryophyllatum) concealed by the side-plates ; outer side-plates very small. 

 Spiracles rarely present. Hydrospires pendent, and opening externally by a 

 series of elongate slits with intervening ridges, distributed in sub-parallel 

 Order on the sloping sides of all the radial sinuses. The slits are only 

 partially covered by the ambulacral plates, and are sometimes visible for their 

 entire length. Lower Devonian ; Spain. Lower Carboniferous ; Europe and 

 North America. 



