THE CRINOIDEA 



i6r 



Glyptocrinus, Hall (1847 ; W. & Sp., 1897 ; synn. Canistrocrinus, W. & 



Sp. ; Pycnocrinus, S. A. Miller), has small BB and arms in zigzag (Fig. XXV.). 



Schizocrinus, Hall (1847 ; W. & Sp., 1881 ; (?) syn. Scyphocrinus, Hall 



non Zenker), doubtful, but close to Glyptocrinus, arms uniserial. Periglypto- 



crinus, W. & Sp. (1897), has large BB and biserial arms. FAMILY 2. MELO- 



CRINIDAE. Melocrinoidea with 4 BB ; in each half-ray 2-5 IIBr ; these 



support 2 or 4 main rami giving off pinnules or pinnulate ramuli ; iBr, 



illBr, and post. IR as in Glyptocrinidae ; tegmen of numerous, small, and 



irregular plates; stem round. Genera Scyphocrinus, Zenker (1833; 



non Hall, nee Pictet), Silurian, Bohemia and (?) N. America. Cup very 



large, including many of the proximal ramuli, which enter the iBr 



and illBr areas ; subsequent rami are free and divergent ; rami and 



ramuli uniserial ; root a large hollow spheroid strengthened by internal 



septa, regarded as a float ( = Camarocrinus) by Hall, as a cystid ( = Lobolithus) 



by Barrande. Mariacrinus, Hall (1859, restr. W. & Sp., 1881-97 ; syn. 



Zenkericrinus, Waag. & Jahn), Silurian, Europe, N. America. Free arms 



composed of wedge-shaped IIIBr, divergent, may or may not bear a 



few ramuli on their amedian sides (Fig. LXXIV. 1). Melocrinus, 



Goldfuss (1826; W. & Sp., 1897; 



synn. Astrocrinus, Conrad ; Turbino- 



crinus, Troost ; Gastanocrinus, and 



Cytocrinus, C. F. Roein. ; Clonocrinus, 



Oehlert), Devonian, Europe and N. 



America ; the 2 main rami of each arm 



are laterally fused into one trunk with 



single large ventral groove ; this bears 



paired biserial pinnulate ramuli (Fig. 



LXXIV. 2) ; thus the genus is related 



to Mariacrinus as Eucladocrinus (p. 158) 



to Platycrinus, and as Steganocrinus (p. 



170) to Adinocrinus. Ctenocrinus, Bronn 



(1840, em. Follmann, 1887), Lower 



Devonian, W. Europe, is distinguished 



by Jaekel (1895), but merged with 



Melocrinus by W. & Sp. (1897); the 



ossicles of the rami are compound, and 

 parVi mnv hpar 2 nitinnlps 



FAMILY 3. PATELLIOCRINIDAE. Melo- 



T ,! -I , < T> nule. Supplementary plates are shaded. 



crmoidea with but few Br incorpor- 



ated in cup ; BB usually 3, unequal, may be the original 5, or may 

 fuse to 1 ; both IBr resemble free brachials ; in each half-ray 1, or 

 generally 2, IIBr, merging into free arms, which may be uniserial, zig- 

 zag, or biserial ; iBr 2-6, a single one rests on RR ; stem small and 

 round. This early Palaeozoic family contains genera with and without 

 additional plates in post. IR ; but all are simple forms, scarcely more 

 removed from the Inadunate type than are the Silurian Adunata. They 

 may be intermediate between Inadunata and some more advanced 

 Camerata, e.g. Clonocrinidae ; but it is not probable that they represent 

 the ancestors of Glyptocrinidae or Melocrinidae. Genera Stelidicorinus, 



FIG. LXXIV. 



Rays of Melocrinidae. 1, Mariacrinus, 



from Brit ' Mus " 57475 - 2 > Melocrinus 

 nobilissimus (after Wachsiuuth & Sprin- 

 Rm, ramus ; r, ramule ; p, pin- 

 shade 



