158 



PALAEONTOLOGY. 



into a few short ramifications like the branches of a shrub, 

 and terminate in irregular and somewhat angular dilations 

 simulating leaves, but which resolve themselves into radiating 

 fasciculi of minute dentinal tubes. There are from fifteen to 



Fig. 69. 

 Magn. section of part of Dendrodus bijporcatus. 



twenty-five or thirty-six of these short and small lateral 

 branches on each side of the medullary rays. 



Such are some of the forms and structures of the fishes 

 that swam in the seas from which were deposited the sedi- 

 ments that have hardened into the "old red sandstones" of 

 Great Britain, Eussia, and other parts of the world. And 

 in this process of consolidation the carcasses of the fishes 



