AGES OF NATURE. 399 



yet found. On the contrary, the Bryozoa, which have long 

 been considered as polyps, but which, according to all appear- 

 s are niollusks of a very low order, are very numerous 

 in this epoch. 



665. The articulata of the palaeozoic age are mostly 

 trilobites, animals which evidently belong to the lower order 

 of the crustaceans (fig. 378). There is an incompleteness 

 and want of 

 development in 

 the form of 

 their body, that 

 strongly re- 

 minds us of the 

 embryo among 

 the crabs. A 

 great many ge- 

 nera have al- Fig. 3'8.Humalonotus delphinocephalus.Konig. 

 ready been dis- 

 covered. The Silurian rocks of Bohemia have yielded up- 

 wards of two hundred species. Homalonotus (fig. 3/8), 

 one of the family Calymenufa, will give a general idea of the 

 form of these palaeozoic crustaceans. Some others seem more 

 allied to the crustaceans of the following ages, but are never- 

 theless of a very extraordinary form, as Eurypterus remipes. 

 There are also found, in the Devonian, some very large 

 entomostraca. The dass of worms is represented only by Nereis 

 and a few Serpula, which are marine worms, surrounded by a 

 solid sheath. The class of insects is entirely wanting. 



666. The inferiority of the earliest inhabitants of our 

 earth appears most striking among the vertebrata. There 

 are as yet neither birds nor mammals. The fishes, and a few 

 reptiles whose fossil foot-marks we only know, are the sole 

 representatives of this division of animals. 



667. The fishes of that early period were not like 

 ours. Some of them had the most extraordinary forms, so 

 tha-; they have been often mistaken for quite different animals ; 

 for example, the Pterichthys (fig. 379), with its two winglike 

 appendages, and also the Coccosteus (fig. 380), of the same 

 deposit, with its large plates covering the head and the ante- 

 rior part of the body. There are also found remains of shark's 

 spines, as well as palatal bones, the latter of a very peculiar 



