AGES OF NATURE. 



199 



most prominent (d). There are also found, for the first 

 time, numerous repre- 

 sentatives of the Cut- 

 tle-fishes, under the 

 form of Belemnites 

 (Fig. 162), an extinct 

 type of animals, sur- Fig. 162. 6 



rounded by a sheath, and containing in their interior a 

 peculiar bone, somewhat similar to the bone of the Sepia, 

 and which commonly is the only preserved part (J). 



487. The variety is not less remarkable among the 

 Radiates. There are to be found representatives of all the 

 classes ; even traces of Jelly-fishes have been made out in 

 the slate of Solenhofen, in Bavaria. The Polyps were 

 very abundant at that epoch, especially in the upper stages, 

 one of which has received the name of Coral-rag. Indeed, 

 there are to be found whole reefs of corals in their natural 

 position, similar to those which are to be seen in the islands 



a 



Fis:. 163. 



of the Pacific. Among the most remarkable types of stony 

 Polyps, may be named the fan-like Lobophyllia (L.flabel- 

 lum, a), and various forms of tree-corals (Lithodendron 

 2iseudostylina, b). But the greatest variety exists among the 

 Echinoderms. The Crinoids are not quite so numerous as 

 in former ages. Among the most abundant are the Pent.a- 

 crlnus (c). There are also already found Comatula-like 

 animals, that is to say, free Crinoids, (Pterocoma pinnata, d). 



