1 82 THE CRINOIDEA 



(1760, synn. Clielocrinus and [?] Calathocrinus, v. Meyer, Flabellocrinus, 

 Klipstein, [?] Cassianocrinus, Laube, [?] Traumatocrimis, Wohrmann, which 

 = Porocrinus, Dittmar non Bill.), Trias, Europe, has 5 minute IBB, a 

 lofty plated tegmen, small tube, but no distinct anal plate. 



Another line of evolution, probably continuing that of the Graphio- 

 crinidae, introduces the Articulate Grade of Dendrocrinoidea, of which 

 the most important family and the first to appear is the FAMILY 9. 

 PENTACRINIDAE. Dendrocrinoidea with pinnulate, uniserial arms, forking 

 once or dichotomising many times, either regularly, or irregularly so that 

 the minor branches become pinnulate ramuli ; with a small, usually 

 depressed patina, in which IBB are often minute or atrophied in adult 

 (pseudomonocyclic, or, as Bigot has recently expressed it, "cryptodi- 

 cyclic ") ; but the flexible tegmen extends some way up the arms, so 

 that the proximal IBr, and sometimes some IIBr, are incorporated loosely 

 in the dorsal cup ; a slight anal tube or cone, but no distinct anal plates 

 in either cup or tegmen ; stem pentagonal or sub-pentagonal, usually 

 with cirri in whorls of 5. Genera Dadocrinus, v. Meyer (1847 ; see v. 

 Koenen, 1887-95), Trias, Middle Europe, has a round or sub-pentagonal 

 stem without cirri, pinnulate arms forking once, 2 IBr, which are united 

 by several small iBr. Holocrinus, W. & Sp. (1886, em. Jaekel, 1893), 

 Trias, Germany, has whorls of cirri, slender arms forking once, 3-4 IBr, 

 not united by iBr, but tegmen stretches up to about IBr, cup high and 

 constricted above. The family characters become more definite in later 

 forms, which may be associated as a SUB-FAMILY PENTACRININAE ; IBB 

 always minute or atrophied ; stem bears cirri in whorls attached to the 

 epizygal of a syzygial pair ; its internodes transversed by 5 ligament- 

 bundles, which are interradially disposed and give rise to a more or less 

 petaloid figure on the joint-faces ; root-attachment may exist in young, 

 but is relinquished in adult (Fig. CL). Genera Pentacrinus, Blumenbach 

 (1804 ; synn. Polycerus, Fischer, 1811, pars; Extracrinus, Austin, 1847 ; 

 [?] Chladocrinus, L. Agassiz; see especially Quenstedt, 1875), Lias and Jura, 

 Europe. Petaloid sectors of stem linear with delicately crenulate edges ; 

 cirri elliptical or compressed in section, in close-set whorls ; IBB present in 

 adult ; RR prolonged downwards over proximal colunmals, the prolonga- 

 tions being jointed ; each arm has at least 4 rami with large pinnulate 

 ramules on one side only. Isocrinw, v. Meyer (1837 ; synn. Isis, Lin- 

 naeus, pars ; Cainocrinus, Forbes ; Picteticrinus, de Loriol ; Cenocrinus and 

 Neocrinus, "Wyv. Thomson ; and Pentacrinus, sensu P. H. Carpenter 1 ), 

 Trias to Recent, now chiefly Caribbean and Pacific. Sectors of stem dis- 

 tinctly petaloid, with coarsely crenulate edges ; cirri circular in section, 

 the whorls further apart (Figs. XVI. 4, 5 ; XVII. 2, 3) ; IBB are visible 

 in various Jurassic species, but become obsolete in later times (cf. Fig. XI.) ; 

 BB may form a complete circlet (on which feature Cainocrinus was based), 

 or may be minute and separated by RR ; IBr 2, non-pinnulate ; arms 

 isotomous or nearly so ; sacculi occur sparingly. See Guettard (1761), 

 J. Miiller (1843), P. H. Carpenter (1884), and Fig. XXIII. 3, 5, on p. 117. 

 Balanocrinus, Agass. in Desor (1845 ; em. de Lor. 1879), Trias to Eocene, 



1 Carpenter chose to ignore all writers on Crinoidea before J. S. Miller. For 

 the history of these names, see Natural Science, April 1898. 



