§ 9. FISHES OF THE DEVONIAN SYSTEM. 763 



small, the longest not exceeding eight or ten inches in 

 length. But in the Devonian system of Russia, gigantic 

 species are met with. I have seen in Sir E. I. Murchison's 

 collection specimens and models in which the lateral spines 

 are one foot in length. 



Coccosteus.* In form, and in the arrangement of the 

 horny scutcheons, the fishes of this genus have a close 

 resemblance to the Pterichthys. The plates are tuber- 

 culated; the tail is very long, covered with scales, and 

 supports a fin. There are four or five species, varying 

 in length from a few inches to two feet. Their remains 

 are the most abundant of the ichthyolites of the Old Red 

 system. Patches of detached scales, and insulated osseous 

 plates, are very frequent in the sandy cornstones and sub- 

 crystalline limestones. They are usually of a brilliant 

 blue or purple colour, which strongly contrasting with the 

 dull red tint of the surrounding rock, renders them easy 

 to be detected. This colour is supposed to be due to the 

 presence of phosphate of iron, which has communicated a 

 similar tint to the ichthyolites of the Caithness schists.f 

 In none of these fishes have any traces of vertebrae been 

 discovered ; it is therefore probable that the spinal column 

 was cartilaginous, as in the Sturgeon. 



Holoptychius. My limits will only admit of a rapid 

 notice of a few other Devonian ichthyolites. Among these, 

 several species of the large sauroid fishes, named Holo- 

 ptychius, from the peculiar character of the scales, are most 

 strikingly conspicuous. This genus we have already 

 noticed in the account of the carboniferous ichthyolites 

 {ante, p. 741).+ 



* Berry-bone fish : from the plates being studded over with small 

 tubercles. Medals of Creation, p. 648. 



f Silurian System, p. 588. 



% A splendid specimen of H. nobilissimus, twenty-eight inches long, 

 is figured in Silurian System, pi. 2, and is now in the British Museum. 



