I 5 6 



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- 

 crinuSy 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. Miiller 

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

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

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

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

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

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

 crinus, Jaekel (18 95, em. Bather, 1897 ; includes Ayriocrinus, Thallocrinus, 

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

 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 IIIBr 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. 

 MARSIPOCRININAE. 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 retwnus, from Bnt. . . * . * . 



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

 i : eteV S ;as T usual b0r x3 f Jaeke1 ' Other M^rsupiocrinus, Phillips, 1839, non de 



Blainville, 1830 ; syn. Cypellocrinus vel 



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

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



IIIBr 



NIBr 



.IBr 



FIG. LXIX. 



