THE CIUNO1DEA 143 





Dicyclic Inadunata came to their acme in Carboniferous times, and only 

 those forms persisted to Neozoic and Recent periods which assumed an 

 Articulate modification, viz. a loose lateral union of proximal brachials, 

 as seen in Pentacrinidae, which are convergents of the Neozoic Flexibilia. 

 The latter sub -order was represented during Palaeozoic times by the 

 Ichthyocrinoidea (Impinnata) ; between them and the Neozoic Apio- 

 crinidae, Bourgueticrinidae, etc. (Pinnata), the links are missing, but may 

 yet be found among Permian and Triassic crinoids (cf. p. 140). At any 

 rate, the Neozoic Flexibilia, when they assumed the free-swimming habit, 

 took a new lease of life and have their acme in our own day. 



The systematic account of the Crinoidea may be prefaced by a table 

 of the terms and symbols employed in technical description, as explained 

 for the most part in the preceding pages. 



PLATES OF PATINA ... . Seepage, 112 



Infrabasal ... IB ,,99 



Basal B ,,99 



Superbasal . SB 159 



Radial. R . 99 



Inferradial Ri . . ,, 112 



Superradial Rs . ,,112 



Radianal . RA ,,119 



Pararadial .PR . . ,,150 



BRACHIALS . free, Br ; fixed, Br . ., 100,112 



Primibrachs . . ,, IBr ,, FBr . ,, 114 



First primibrach . IBi'j . . ,, 115 



Second primibrach . IBr 2 . . ,, 115 



Primaxil . . . lAx . . ,, 114 



Secundibraclis . . ,, IIBr ,, IIBr . ,, 114 



Secundaxil . . IIAx . ,, 114 



Tertibrachs . . . IIIBr . 114 



Quartibrachs . . . IVBr . ,,114 



and so on to the 



Finials . F ,, 115 



AMBULACRALS . . . Amborc.p. . ,, 100,115 



Primambulacs . . . lAmb . . ,, 115 



Secundambulacs . . IIAnib . ,, 115 



and so on. 

 INTERRADIAL AND SUPPLEMENTAL" 



ELEMENTS . . . . . ,, 109 



An interradius . . IR . . ,,20 



Iiiterbrachials . . . iBr ,, 118 



Intersecundibraclis . illBr . . ,, 118 



and so on. 

 Special anal plate (or proximal 



median plate of anal tube) . x ,, 119 



Proximal tube-plate on right rt . ,, 121 



Corresponding plate on left .It . ,, 121 



Deltoids . . .A . . ,, 100 



here regarded as homologous with 



Orals . . . -9 ,, 124 



Interambulacrals . . iAmb . . ,, 118 



Interprimambulacs . ilAmb . . ,, 118 



Intersecundambulacs . illAmb . . ,, 118 



The various radii and interradii are denoted as explained in the table 

 on p. 110. 



