68 



VERTEBRATA. 



behind the former. The ventral fins are nearer the tail than in any other 

 ganoid. This splendid specimen, one of the ornaments of the British Mu- 

 seum, was discovered in the Old Red Sandstone at Clashbinnie, Scotland, and 

 is figured in Murchison's " Silurian System." The creature lies on its back. 

 " The body (says Hugh Miller) measures a foot across by two feet and a half 

 in length, exclusive of the taii, which is wanting; but the armor in which it 

 is cased might have served a Crocodile or Alligator of five times the size." 

 The head is short and obtuse; the lower jaw, the mouth, and the two branchial 

 rays or plates are exposed. The scales are very large and deeply wrinkled. 



Size, 2 ft. 9 in. X 4 in. 



No. 106. [313J Cephalaspis Lyellii, Agassiz. 



Body and Head, on slab (cast). This famous 

 Devonian Fish is placed among the Placoganoids. 

 The first specimen of this genus was discovered 

 by Hugh Miller. The most striking feature is 

 the enormous buckler (made up of plates usually 

 hexagonal) covering the head and prolonged 

 backwards into lateral points. The head com- 

 prises fully one-third the creature's entire length. 

 The body was protected by plates arranged trans- 

 versely, and the tail carried a heterocercal fin. 

 The dentition is unknown; but the mouth was 

 probably placed beneath the head and suctorial, 

 as in the Sturgeon. The eyes were placed closely 

 together near the middle of the head. This fos- 

 sil, now in the British Museum, was found in the 

 Old Red Sandstone in Forfarshire, Scotland. 



Size, 9x5. 



No. 107. [1303] Cephalaspis Dawsoni, Lankester. 



In this species the head is proportionately very large, and the body seems 

 to have been covered with very fine tubercles. 

 From the Lower Devonian at Gaspe, Canada. 



No. 108. [311] Rhizodus Hibberti, Owen. 



Lower Jaw, left ramus (cast). The generic term Bhizodus is applied to 

 those ganoids of the Coal Measures whicli have stout serial teeth and slender 

 laniaries. The great strength of the cephalic plates and of the jaws and teeth 

 shows that this was a powerful carnivorous fish. Prof. Newberry has recentlj' 

 named an equallj' large species {R. anceps) from the Mountain Limestone of 

 Illinois. The genus seems characteristic of the Lower Carboniferous. This 

 fragment of the lower jaw was disinterred from the Carboniferous Limestone, 

 near Edinburgh, and is in the British Museum. Size, 19 x 7. 



