PLAC0GAN01DEI. j 49 



degree, in some of the other genera of the old red, such as 

 the Pterichthyes and Asterolepicles. " From the snout of the 

 Coccosteus down to the posterior termination of the dorsal 

 plate the creature was cased in strong armour, the plates of 

 which remain as freshly preserved in the ancient rocks of the 

 country as those of the Pimelodi of the Ganges on the shelves 

 of the Elgin museum ; but from the pointed termination of 

 the plate immediately over the dorsal tin to the tail, com- 

 prising more than one half the entire length of the animal, 

 all seems to have been exposed, without the protection of 

 even a scale; and there survives in the better specimens 

 only the internal skeleton of the fish and the ray-bones of the 

 fins. It was armed, like a French dragoon, with a strong- 

 helmet and a short cuirass ; and so we find its remains in the 

 state in which those of some of the soldiers of Napoleon's old 

 guard, that had been committed unstripped to the earth, may 

 be dug up in the future on the fatal field of Borodino, or along 

 the banks of the Dwina or the Wap. The cuirass lies still 

 attached to the helmit, but w r e only find the naked skeleton 

 attached to the cuirass. The Pterichthys to its strong helmet 

 and cuirass added a posterior armature of comparatively 

 feeble scales, as if, while its upper parts were shielded with 

 plate-armour, a lighter covering of ring or scale armour 

 sufficed for the less vital parts beneath. In the Aster olepis 

 the arrangement was somewhat similar, save that the plated 

 cuirass was wanting. It was a strongly-helmed warrior in 

 slight scale-armour ; for the disproportion between the strength 

 of the plated head-piece and that of the scaly coat was still 

 greater than in the Pterichthys. The occipital star-covered 

 plates are, in some of the larger specimens, fully three- 

 quarters of an inch in thickness, whereas the thickness of the 

 delicately-fretted scales rarely exceeds a line. 



"Why this disproportion between the strength of the 

 armature in different parts of the same fish should have 



