Tin Coiiiiinj of Vertebrates awl ///*> <>/' Wxlies 





One of the oldest North American species 

 of these armored fishes is that known as 

 Palaeaspis, in which the front part of the body 

 is covered by plates much as if it had been 

 shut in between clam-shells, with an extra, 

 narrow plate along either side and a small one 

 over the nose. The back portion seems to 

 have been naked at least no scales or plates 

 have so far come to light, and it does not seem 

 to have borne a spine like its near English 

 relative Pteraspis. 



Just above this comes the curious Ceph- 

 alaspis, with a broad, rounded head, some- 

 thing like a saddler's knife in shape, and 

 the balance of the body clad in a few series 

 of rather long and narrow interwoven plates. 

 On either side of the head is a little flap 

 that suggests some kind of a fin, but is sup- 

 posed to have really covered the outlet of 

 the gills. 



The wingfish, Pterichthys, and its North 



were voluntary acts, and many there be who succumb to this 

 temptation. But these characters have been brought about, so it 

 is believed, by elimination, by the weeding out of the more 

 defenseless, so that the process is passive, not active. 



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