THE CRINOIDEA 



183 



has columnals of circular or basaltifonn section, with crenellations round the 

 edge only, not along the sides of the sectors. Austinocrinus, de Loriol (1889), 

 Cretaceous ; columnals have a joint-surface like that of Isocrinus, but with 

 finer striae radiating from the petals to the circular periphery. Metacrinus, 

 P. H. Carp. (1884), W. Pacific, differs from Isocrinus in having 5-8 IBr, 

 of which IBr 2 and 3 always, and IBr 5 an(i 6 usually, are united by syzygy, 

 while each, except IBr x and the hypozygals, bears a pinnule ; BB form a 

 complete circlet. The members of this sub-family live in colonies, but 

 can move about and anchor by the cirri at the distal end of the stem. 



10 



FIG. CI. 



Pentacrininae. 1, 1'entncrinus fossil is, portion of stem, patina, and portion of arm, showing 

 rami, ramuli, and pinnules (p). 2, the same ; portion of a cirrus and articular facet of a cirral. 

 3, the corresponding parts of Isocrinus asteria. 4, Mctacrinus Moseleyi, cup and proximal por- 

 tion of an arm. 5, ImrfMMJKiuitdKt. cup seen from below, with portion of stem, bearing cirri, 

 still attached to it, and with proximal brachials. 6, a radius of the same, showing isotomy of arm. 

 7, Isocrinus amblyscalaris, joint-surface of an internodal columnal. 8, the same of Jtalanocrinus 

 mtbteres. 9, the same of Pentacrinus fossiii*. 10, the same of Isocrinus asteri.a. (From Bather, 

 after P. H. Carpenter, de Loriol, von Meyer, and original.) 2, 3, 7, 8, 0, and 10 are slightly 

 enlarged. 



The stem is least specialised in Balanocrinus, most in Pentacrinus, in 

 which it attained a length of 18 feet (Quenstedt thought 70). FAMILY 

 10. UINTACRINIDAE. Dendrocrinoidea in which the arms fork once on 

 IBr.,, are long and pinnulate, with numerous syzygies, and are incor- 

 porated in their proximal regions, together with proximal pinnules, in 

 the dorsal cup, by means of iBr, illBr, and interpinnulars ; there is 

 no stem, but a centrale. Genus Uintacrinus, Grinnell (1876), Upper 

 Cretaceous, N. America, Germany, and England (Fig. GUI.), has a rela- 

 tively large flexible theca and long arms. It was free-swimming and 

 possibly pelagic. IBB usually obsolete. For detailed account, see Bather 

 (1896). FAMILY 11. MARSUPITIDAE. Dendrocrinoidea (?) with pinnulate 



