68 GANOID FISHES OF OLD RED SANDSTONE. 



entire absence of any remains of it, seems to have been composed 

 of soft cartilage. In the Cephalapsis (or buckler-head), the head 

 was very large in proportion to the body, occupying one-third of 

 its length, and being rendered of enormous breadth by two cres- 

 cent-shaped wings, extending backwards and outwards. In the 

 Ptericthys (or winged fish), the plates both of the head and body 

 were very large, and consequently few in number ; it was fur- 

 nished with a pair of wing-like fins, placed far forwards, and 

 terminating in a kind of hook, or strong curved point ; and the 

 tail, which occupied more than a third of the total length of the 

 animal, was straight, pointed, and covered with small tubercu- 

 lated angular scales. " Most probably the tail was employed as 

 the principal organ of locomotion ; the pointed fins being elevated 

 at the approach of danger, and the animal in this way rendering 

 itself as unapproachable and as difficult to be swallowed as its 

 form would admit of." The Cocosteus had a body of triangular 

 shape, tapering away towards the tail ; and was covered almost 

 entirely by a central plate, much larger than any of the others, 

 having a continuous ridge along the middle of the back ; it was 

 also furnished with a couple of defensive fins, situated near the 

 head, like those of the Ptericthys. The tail evidently possessed 

 a vertebrated structure ; and it was by this that the animal was 

 most certainly recognised as a Fish. its jaws and teeth having 

 more the characters of the nippers of a Lobster or the mandibles 

 of a Beetle. The teeth were chiselled, as it were, out of the 

 solid bone of the jaw; just as the teeth of a saw are cut out of 

 a plate of steel : and the line of opening of the jaws was vertical, 

 as in the Articulata, instead of being horizontal, as in the Verte- 

 brata. Remains of this fish are found very abundantly in some 

 situations ; varying from a few inches to two feet in length. 

 The other Fishes of the Palaeozoic epoch were, for the most part, 

 less widely different from those of the present day ; one remark- 

 able genus may be mentioned, the Holoptychius, which exceeded 

 most of the others in size, and was evidently adapted to prey 

 upon them. The name of this fish is derived from the large 

 undulating furrows marked upon the surface of its enamelled 

 scales, which give them a most beautiful appearance ; these scales, 



