THE CRINOIDEA 



GROUP A. FAMILY 1. PLATYCRINIDAE. No anal. BB 3 (= 2 fused 

 pairs and 1 unfused, this being usually the left, sometimes the right, 

 antero-lateral) forming a pentagon. Cordylocrinus, Hapalocrinus, Cocco- 

 crinus t and Cylicocrinus, which appear in the Silurian and continue to 

 Devonian, are more primitive than the rest. Marsipocrinus, though also 

 Silurian, is considerably more advanced, and may be regarded as a 

 first attempt at the typical Platycrinus structure ; it was apparently an 

 unsuccessful attempt, since it left no descendants, although Wachsmuth 

 & Springer and Jaekel seem to regard Platycrinus as such. Platycrinus 

 came in the Carboniferous, with its offshoot Eucladocrinus, and, unless 

 we are to imagine a reversal of the general trend of evolution, must be 

 derived from a simpler form than Marsipocrinus. These facts are best 

 presented by instituting 3 sub-families. SUB-FAMILY 1. COCCOCRININAE. 

 Platycrinidae with IBr 2 (3 in Hapalocrinus Victoriae) ; IIBr more than 

 2 ; few Amb and iAmb in tegmen ; (?) anal tube rarely present ; stem cir- 

 cular in section ; lumen small and round. Genera Coccocrinus, J. M tiller 

 (1855, syn. Amblacrinus, d'Orbigny pars, 1849), Silurian of America, 

 Devonian of Europe ; O large, symmetrical, almost covering the tegminal 

 ambulacra ; iAmb 1 or 3 ; anus between O and iAmb ; arms apparently 

 delicate, fork once, distal portions unknown. Cylicocrinus, J. Miiller 

 (1855, as Culicocrinus; Jaekel, 1895), Devonian, Germany (Fig. XL.), 

 differs from' Coccocrinus chiefly in having heavy biserial arms. Hapalo- 

 crinus, Jaekel (1895, em. Bather, 1897 ; includes Agriocrinus, Thallocrinus, 

 and Clematocrinus, Jaekel), Silurian of England, Australia, and (?) N. 

 America, Devonian of Germany (Fig. LXIX.) ; small ; iAmb more than 



1 ; Amb visible between and iAmb ; 

 arms fork once, sometimes twice, varying 

 in this respect in the same species, or even 

 individual ; IIBr (and IIlBr when pre- 

 sent) uniserial, or slightly in zigzag, bear- 

 ing alternately disposed pinnules, either 

 on each or on every other Br ; cirri at 

 the root, and often on nodals. Cordylo- 

 crinus, Angelin (1878 ; W. & Sp., 1897 ; 

 Bather, 1897), Silurian of Gotland and 

 England, Lower Devonian of N. America ; 

 differs from Hapalocrinus in having com- 

 pound IIBr, each of which bears a pin- 

 nule on each side. SUB - FAMILY 2. 

 MARSIPOCKININAE. Platycrinidae with 

 one IBr ; IIBr, if not finials, one or two ; 

 many Amb and iAmb in tegmen ; no 

 anal tube; stem circular in section; lumen 

 large and quinquelobate. Genus Mar- 



Hapalocrinus retiarius, from Brit. . e . .. ^ ,, ... 



Mus. E5615. c, cirri; iBr, interbra- sipocrinus, Bather (1889, nom. nov. pro 



Marsupiocrinus, Phillips, 1839, non de 

 Blainville, 1830 ; syn. Cypellocrinus vel 

 Cupellaecrinus, Shumard, 1866, ex Troost MS., non Steininger), Silurian, 

 N.-W. Europe and N. America ; arrangement of cup-plates shown in Fig. 



