THE CRINOIDEA 191 



developed, but are absent from Sagenocrinus. Otherwise the two genera 

 agree closely. 



The following genera are placed provisionally in the Impinnata : 

 Edriocrinus, Hall (1859), Devonian, N. America (Fig. CXII.), when young 

 is attached by BB, but is 

 free - floating in adult ; BB 

 become fused into a bowl- 

 shaped mass, supporting 5 

 RR and x ; arms broad, with 

 low Br, isotomous. Cleio- 

 crinus, E. Billings (1856 ; see 

 W. & Sp., 1886), Ordovician, 



Canada ; IBB and BB hidden V F JG . cxn. 



by stem ; RR small and sepa- I Edriocrinus pirtfornis, nat. 



rated by a large pentagonal size. (After Hall.) i, from 



. , . , . v side, showing concavity for 



interradial ; arms isotomous to \ J*J attachment at end of fused 



about VIIBr, and all appear \^-B basais (B). 2, the cup from 



above, showing anal (x) and 

 to interlock and to be joined facets of radiais. 



by close suture ; post. IR sup- 

 ports a vertical series of anals, which reach the full length of the arms. 

 Rliopalocrinus, W. & Sp. (1879), is based on " Taxocrinus gracilis" 

 Schultze, Devonian, Eifel ; it perhaps belongs to Dicyclica Inadtinata. 



GRADE 2. Pinnata. 



Flexibilia with BB and RR united by close suture, RR and proximal 

 Br by muscular articulation or syzygy ; pseudomonocyclic ; arms pinnu- 

 late and either simple or isotomous ; axial canal separate from ventral 

 groove throughout ; lax is generally IBr , rarely IBrj ; 5 O present in 

 early stages and sometimes in adult, but usually atrophy ; anals do not 

 form part of the dorsal cup in the adult. Stem round, pentagonal, or 

 elliptical in section, proximal columnals often forming a widened cone. 



This group is confined to Mesozoic and later times, and there is no 

 evidence that it is descended from the Palaeozoic Impinnata ; it may be 

 an offshoot from Triassic Dicyclica Inadunata, from which it is dis- 

 tinguished by the mode of growth of the proximal columnals. 



FAMILY 1. APIOCRINIDAE. Pinnata in which the patina consists of 5 

 BB and 5 RR ; arms incorporated to a very variable extent in the cup, 

 and iBr may be present ; columnals round or pentagonal in section, their 

 joint-surfaces marked with radiating striae, and sometimes tubercles in the 

 middle ; no cirri ; root, when present, encrusting. (For fossil forms, see 

 de Loriol, 1883.) Genera Millericrinus, d'Orb. (1840 ; synn. Ceriocrinus 

 and Pomatocrinus, Desor ex Konig), Trias (?) to Lower Cretaceous, Europe ; 

 IBr 1 united to R by muscular articulation, and to lax by close suture ; arms 

 isotomous, free from IBr, or proximal Br united by tegmen, or a few small 

 iBr developed ; except for the proximale, the upper columnals are rarely 

 widened (Fig. XVII. 7). In some species (Fig. LII.) the crown breaks off 

 from the root, the stem is gradually resorbed, and a free-floating stage attained. 

 Apiocrinus, Miller (1821), Jurassic, Europe; IBr x united to R probably 

 by ligament, not by muscular articulation, and to lax by incomplete 



