THE CRINOIDEA 



161 



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 IlBr ; 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 ( = Camarocrmus) by Hall, as a cystid ( = Lobolithus) 

 by Barrande. Mariacrinus, Hall (1859, -estr. 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 ; Castanocrinus, and 

 Cytocrinus, C. F. Roem. ; 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 

 each may bear 2 pinnules. 



FAMILY 3. PATELLIOCRINIDAE. Melo- ger). Rm, ramus ; r, ramule ; p, "pin- 

 . 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, 



ii 



FIG. LXXIV. 



Rays of Melocrinidae. 1, Mariacrinus, 

 from Brit. Mus. 57475. 2, Melocrinus 

 nobilissimus (after Wachsiuuth & Sprin- 



