DEVONIAN AND OLD RED PERIOD. 



147 



Devonian. There are also a few forms of Phyllopods (Es- 

 theria). Taken as a whole, the Crustacean fauna of the 

 Devonian period presents many alliances with that of the 



Fig 88 Devonian Trilobites. a, Phacops latifrons, Devonian of Britain, the Con- 

 tinent of Europe, and South America ; 6, Homalonotua armatus, Europe ; c, Phacop* 

 (Trimerocephalus') Icevts, Europe; rf, Head-shield of Phacops (Portlockia) granulatus, 

 Europe. (After Salter and Buianeister.) 



Upper Silurian, but has only slight relationships with that of 

 the Lower Carboniferous. 



Besides Crustaceans, we meet here for the first time with 

 the remains of air-breathing Articulates, in the shape of Insects. 

 So far, these have only been obtained from the Devonian 

 rocks of North America, and they indicate the existence of at 

 least four generic types, all more or less allied to the existing 

 May-flies (Ephemeridce). One of these interesting primitive 

 insects, namely, Platephemera antiqua (fig. 89), appears to have 

 measured five inches in ex- 

 panse of wing; and another 

 (Xenoneura antiquorum} 

 has attached to its wing the 

 remains of a " stridulating- 

 organ " similar to that pos- 

 sessed by the modern Grass- 

 hoppers the instrument, as 

 Principal Dawson remarks, 

 of " the first music of living Fig. 89. Wing of Platephemera anti- 



things that Geology as yet ^- Devonian, America. (After Daw- 



reveals to us. " 



Amongst the Mollusca, the Devonian rocks have yielded a 



