254 PAL/KONTOLOGY 



latter the arm-branches are closely packed together, the 

 anal tube is compressed and its plates are wider 

 than high. 



Petalocrinus (Sil., marking a definite zone) has the 

 branches of each arm united into a fan-like body. 



Woodocrinus (Fig. 71, f), of which beautiful examples 

 are found in the Carboniferous Limestone of the North 

 of England, is a dicyclic inadunate with four-branched 

 short arms and a relatively short stem tapering to a point. 



Among Camerata, Amphoracrinus has been described. 

 Actinocrinus is similar, but with the superficial area of the 

 tegmen not larger than that of the cup, and a longer and 

 central anal tube. A very remarkable genus is Euca- 

 lyptocrinus (Fig. 71, e, Sil.-Dev.), with the base deeply 

 concave, the visible part of the cup being mainly com- 

 posed of brachials and interbrachials : the arms bifurcate 

 within the cup, and from the ten sets of interbrachials 

 there grow up vertical pillars which arch out and meet 

 at their upper ends, forming ten niches in which the 

 arms lie when not spread out. There are a few dicyclic 

 camerates, of which Rhipidocrinus (Dev.) and Rhodocrinus 

 (Carb.) may be mentioned. 



The few Palaeozoic Flexibilia are dicyclic and impin- 

 nate (i.e., arms have no pinnules) : Taxocrinus (Fig. ji,d, 

 Sil.-Carb.) is the commonest. The best-known Triassic 

 crinoid is Encrinus (Figs. 70, e ; 71, i), which seems to be 

 related to Carboniferous inadunates such as Woodocrinus. 

 It is dicyclic, but the infrabasals are minute and difficult 

 to find. 



Isocrinus (Fig. 70,7, Trias.-Rec.) and Pentacrinus (Jur.). 

 not only have minute infrabasals, but the basals are very 

 small, and the radials intervene between them and come 

 into contact with the stem, so that the whole cup, lying 

 between a large stem and large, much-branched and 

 pinnulate arms, is reduced to insignificance. The stem 



