ROOM V. CEPHALASPIS LTELLII. 423 



that the spinal column was cartilaginous, as in the Stur- 

 geon. 



CEPHALASPIS LYELLII. There are some very fine examples 

 of this singular genus of small fishes, in the first division of 



LIGX. 84. CEPHALASPIS LYELLII; FROM GLAMMIS, FORFARSHIRE. 

 ($ not. size.) 



Case A, on the left of the entrance from Room IV., that were 

 presented by the eminent geologist commemorated in the 

 specific name ; they will be easily recognised by the figure, 

 Lign. 84. * The most striking feature in these Ichthy elites is 

 the enormous scutcheon, or buckler, which forms the head, 

 and is prolonged posteriorly into two lateral horns or points ; 

 this part so closely resembles the cephalic shield of certain 

 trilobites, that the first specimens were supposed to be the 

 remains of unknown crustaceans ; the name Cephalaspis 

 (buckler-head^) is derived from this character. This remarkable 

 appearance is occasioned by the intimate anchylosis of all the 

 bones of the cranium. The body of these fishes is relatively 

 smaller than the head, has but one dorsal fin, and terminates 

 in a tail with a long pedicle, supporting a fin. There are two 

 very small eyes placed towards the middle of the head. The 

 body is covered with rhomboidal scales, and the head with 



1 The first fish of this genus was discovered by Mr. Hugh Miller, in 

 whose charming little work, "New Walks in an Old Field," will be 

 found a most graphic description of the Devonian Ichthyolites. I know 

 not a more fascinating volume on any branch of Natural History. 



