1 68 THE CR1NOIDEA 



periphery like spokes of a wheel ; iBr may or may not join iAmb ; 

 illBr often present Dizygocrinus, W. & Sp. (1897), like Eutrocho- 

 crinug, but with rounded calyx, more variable in composition, anal tube 

 and stem rather slender. Hyperocrinus, Meek & Worthen (1865, as 

 Uperocrinus; syn. Lobocrinus, W. & Sp., 1897); 18-22 free rami, arranged 

 in arm-groups, separated by iBr which join iAmb ; illBr sometimes 

 present ; lofty tegmen ; respiratory pores unknown, flfacrocrinus, W. 

 & Sp. (1897) ; 12-16 rami, in groups, but not separated by iBr 

 except in post. IR ; anal tube tapering ; stem slender ; tegmen coni- 

 cal or hemispherical ; respiratory pores, 10. The study of the relations 

 between these genera is a fertile and unappropriated field. 



FAMILY 7. PERIECHOCRINIDAE. Batocrmoidea with 3 BB ; IBi^ 

 hexagonal; each half-ray contains 1-5 IIBr, and sometimes 2-6 IIIBr ; 

 free arm -rami biserial, usually branching ; iBr numerous and merging 



FlO. LXXX1I. 



Batocrinus. 1, B. ii'nsidtictylus, calyx from the side (after Casseday, nat. size). 2, cup 

 seen from aboral side, from Brit. Mus. B5055. Supplementary plates shaded, x J. 



into iAmb ; post. IR wide, with plates in successive rows of 1,3, 4-6, etc. ; 

 tegmen of numerous small plates in which O, Amb, and radial dome-plates 

 are sometimes to be distinguished, especially post. O ; anus without tube, 

 from sub-central to marginal ; stem large, round, with wide lumen, round 

 or 5-lobed. Members of this family, esp. Gennaeocrinm, are liable to be 

 confounded with Actinocrinidae, but differ in the presence of 3 plates 

 (not 2) in the second row of post. IR, in which respect they resemble 

 Xenocrinidae, Carpocrinidae, Coelocrinidae, and Batocrinidae. Genera 

 Periechocrinus, Austin (1843 ; synn. Geocrinus, d'Orbigny ; Saccocrinus, 

 Hall ex Troost ; Pyxidocrinus, J. Muller, pars ; [?] Trochocrinus, Portlock 

 and [?] Pander ; [?] Pradocrinus, Verneuil, 1850 ; see W. & Sp., 1897), 

 Silurian to Carboniferous, Europe, N. America, Australia ; elongate cup 

 of thin long plates, usually with axial folds, and depressed theca in which 

 are not distinguishable ; arms fork and are less advanced than in 

 Abacocrinus (p. 165). Beyrichocrinus, Waag. & Jahn (1899), Silurian, 

 Bohemia, little known. Megistocrinus, Owen & Shumard (1852 ; W. & 

 Sp., 1897), Devonian and Carboniferous, N. America, (?) Carboniferous, 



