NATURAL HISTORY OF THE PRIMEVAL WORLD. 



wards ; one of tlie legs cut away at tlie Iiip-joiiit, and 

 the other, as if to preserve the balance, placed directly 

 under the centre of the figure which it seems to sup- 

 port. Such, at a first glauce, is the appearance of the 

 fossil iu its sandstone bed. 



The body was of very considerable depth, perhaps 

 little less deep proportionally from back to breast than 

 the body of the tortoise ; the under part was flat, the 

 upper rose towards the centre into a roof-like ridge. 



lies of the Dovonian epoch. 1, Coccnstens, one-third natural size; 2, Ptericllthys. 

 one-t'ouith natural size; 3, Cephalaspis, one-fouith natiiial size. 



and both under and upper were encased in a strong 

 armour of bony plates, which, resembling those of the 

 tortoise more closely than those of the crustacean, 

 received their accessions of growth at the sutures or 

 edges. 



On the underside the plates are divided by two lines 

 of suture, which i-un, the one longitudinally through 

 the centre of the body, the other transversely, also 

 throvigh the centre of it: they bisect one another at 

 right angles, but a lozenge-shaped plate intervenes at 

 the point of bisection. 



There are thus five plates at the lower or belly part 

 of the animal, all thickly tuberculated outside with 

 wart-like protuberances ; tlie imier present appearances 

 indicative of a bony structure. 



The plates on the upper side are more numerous 

 and less easily described ; just as it woidd be difficult to 

 particularize the forms of the various stones which com- 

 l>ose the ribbed and pointed roof of a Gothic cathedral ; 

 the arched ridge or hump of the back requiring, in a 

 somewhat similar way, a peculiar form and arrange- 

 ment of the plates. 



A stout plate, of hexagonal form, covers and protects 

 the apex of the ridge, like a skull-cap or lielmet; and 

 nearly corresponds in position to the flat central part of 

 the under side. Ai'ound it runs a border of variously- 

 formed plates, diminishing iu size and increasing in 

 number towards the head, and separated, like the 

 different portions of a dissected map, by deep sutures. 

 All present a tuberculated surface. The eyes are fixed 



in front, on a prominence nnich lower than tlie roof- 

 like ridge of the back. As in many other fishes, the 

 mouth seems to have opened in the edge of the crea- 

 ture's snout, where a line traversing the back would 

 bisect a line traversing the belly. The two arms or 

 paddles are placed so far forward as to give the body a 

 disproportionate and decapitated appearance. From 

 tlie shoulder to the elbow, so to speak, occurs a swell- 

 ing muscular projection, as in the human arm ; tlie part 

 below is flattened so as to resemble 

 the blade of an oar, and terminates in 

 a strong sharp point. The tail is of 

 considerable length, more than equal 

 to a third of the entire figure, and of 

 an angular form — the base represent- 

 ing the part attached to the body, and 

 the apex its termination. It was 

 clothed with small tuberculated rhom- 

 boidal plates, like scales ; and where 

 the internal structure is shown, appear- 

 ances may be seen of a vertebrated 

 bone, with rib-like processes standing 

 out at a sharp angle. 



From this life-like description the 

 reader will readily image to himself the 

 actual aspect of the Pterichthys. Its 

 jointed arms, or paddles, were em- 

 ployed in swimming; and its speed, 

 combined with its defensive armour, 

 must have rendered it a formidable 

 denizen of the Devonian seas. 



The Cipliahisji/s, or Buckler-head, 

 bore a considerable resemblance to 

 the fislies of the present titue. It was protected only 

 on the anterior part of the body; its head-plate 

 consisting of a single piece, shaped like a shield, whence 

 its scientific appellation. 



Other fishes of the period were undefended by any 

 such armour as that wliich we have described, but the 

 strong resisting scales that enveloped the whole bo<ly 

 afforded, nevertheless, a considerable protection. Such 

 were the Acanthodians, whose fins were armed and 

 supported by sharp spiny bones ; the Climatius ; the 

 Diplacantlius ; the Diptents, or doulile-finned ; the 

 Osteolcpis, or bony-scale; the Ilolcjiti/chiiis, or all- 

 wrinkle, so named in allusion to the curious wrinkle- 

 like engraving on its large enamelled scales; and 

 the AsU:rolepis, or star-scale. 



The head of the latter was encased in bony plates, 

 fretted with star-like tubercles (whence the name) ; and 

 its body was covered with bony scales, not less beauti- 

 fully sculptured than the marbles of Nineveh. Even 

 the elaborate carvings of Benvenuto Cellini seem rude 

 and unfinished compared with those which fretted the 

 armour of this inhabitant of the Devonian ocean. It 

 was a fish of large size, equalling in tliat respect, and 

 sometimes surpassing, a large porpoise. Its vertebral 

 column is supposed to have been cartilaginous, like 

 that of the sturgeon ; its teeth partook of the characters 

 both of the fish and the reptile classes — the outer row 

 being thickly set, as in the fish, while the inner was 

 thinly set, as in the reptiles. 

 In reference to these species, however. Dr. Pugo 



