RAMBLES AND REVERIES. 



different angles. Poteriocrimts crassus (Fig. 15) is 

 one of the most frequently occurring of the Derby- 

 shire encrinites. The body or "head " is tapered in 

 shape, thus resembling the little Rhizocrinus Lofo- 

 tensis which has been dredged up alive from the 

 depths of the North Sea by Dr. Carpenter and Sir 

 Wyville Thompson. In other respects, however, 

 Rhizocrinus finds affinities with an ancient race of 

 crinoids which flourished in 

 Jurassic times, and of which 

 Apiocrinus rotundus is a con- 

 spicuous specimen (Frontis- 

 piece). Other carboniferous 

 crinoids are the genera 

 Actinocrinus, Cyathocrinus, 

 Gilbertocrinus, Taxocrinus, 

 Woodocrinus, Platycrinus. 

 Numerous as are the British 

 Carboniferous encrinites, 

 they occur in still vaster 

 numbers in North America. 

 Very few occur in the Permian strata. This does 

 not mean that they had died out, for they reappear 

 in large numbers in later epochs. 



The Secondary encrinites are not so numerous as 

 the Primary, but they are, in the main, of a higher 

 type. The encrinites of the Secondary rocks mainly 

 differ from those of the Primary in not having the 

 grooves of the arms arched over, but the mouth 

 and the grooves concerned in obtaining food were 

 open to the surface and continuous, whereas the 



FIG. 15. 

 Head of Poterwcrimig. 



