FISH. 



FISH. 



The following description of aome of these fishes, from ProfoHor 

 Ansted's picturesque .Sketches of Creation,' will give the general 

 reader an idea of the formi assumed by some of the extinct fishe* 

 of our own island : 



" The tribe of existing PUooid Fishes most resembling those whose 

 remain* are found foasil. is that of which the Sharks are the well- 

 known repreaentativea. These powerful and rapacious animals, which 

 are at this day the tyrants of the deep, seem to have been, when first 

 introduced, of small size, and were accompanied by some few species 

 of the next or Ganoid order. Only nine species of these Shark-like 

 monsters hare yet been determined with certainty from the Silurian 

 and Devonian rocks, and of these two only are from the former. It 

 is chiefly the Oanoid Fishes whose remains are handed down to us in 

 the Old Red-Sandstone and other rocks of that period. Sixty distinct 

 species of these fishes have been mentioned ; and almost all of them 

 are known from British specimens. Most of them are remarkable for 

 exhibiting strange peculiarities of shape, approximating them in some 

 instances to the structure of the lower orders of animals, combined 

 with some apparent affinities to the class of reptiles. The most 

 remarkable group of these fishes contains several genera, three of 

 which will require special notice : they are the Cephalatpit, or 

 Buckler-Headed ; the Pterichlhyi, or Wing-Fish ; and the Coccottetu, 

 so called from the berry-like tubercles with which its bony scales are 

 covered. 



" The most extraordinary part of the first of these fishes, the 

 Buckler-Headed, is the head, from which its name is taken. This 

 has been compared to the crescent-shaped blade of a saddler's cutting- 

 knife, the body forming the handle. It is extremely broad and flat, 

 extending on each side considerably beyond the body, and the bones 

 appear to have been firmly soldered together, so as to form one shield, 

 the whole head being thus apparently covered by a single plate of 

 enamelled bone, and when seen detached from the body, hardly to be 

 distinguished from the head of a trilobite. The body, compared with 

 this singular head, appears extremely diminutive ; the back is arched, 

 and gradually recedes in elevation towards the tail, which is of mode- 

 rate length ; the fins are few in number, and not very powerful, but 

 appear to have possessed a bony ray in front, the rest of the fin being 

 more fibrous. The whole body was covered with scales, which varied 

 in shape in different parts, and seem to have been disposed in series. 

 This fish never seems to have attained a large size, the best preserved 

 specimen having only a length of seven inches, with a breadth of three 

 inches between the points of the crescent-shaped buckler. It has 

 been supposed by Professor Agassiz that the singular shape of the 

 head served as a defence to this animal in case of attack ; and one 

 can readily imagine that the soft substance of the Orthoceratites, 

 probably the largest and most formidable of its enemies, would be 

 injured by any attempt to swallow so singular and knife-like an animal 

 as the one before us. Like many and indeed most of the species 

 belonging to the Qanoid order of fishes, and common in the older 

 rocks, the bones of the head and the scales of this strange monster 

 were composed internally of a comparatively soft bone, but each was 

 coated with a thick and solid plate of enamel of extreme hardness, 

 and almost incapable of injury by any ordinary amount of violence. 

 The detached scales, the buckler bead, and sometimes the complete 

 outline of the animal have thus been able to resist destruction, and 

 are found in sandy rocks composed of such coarse fragments that 

 their accumulation would seem to have been accompanied with vio- 

 lence sufficient to have crushed to powder almost any remains of 

 organised matter, and from which indeed we never obtain any frag- 

 ments of shell* or other easily-injured substances. The remains of 

 this tish have been found in Herefordshire and many parts of Wales, 

 as well as in Scotland, and lately also in Russia ; but the animal was 

 strictly confined to the period of the Old Red-Sandstone, though it is 

 not easy to giu>n what may have been its habits, in what depth of 

 water it preferred to live, or in what way it obtained its food. 



" The Pleneklhyi is even more strikingly different from any existing 

 prcies of animal than the singular monster we have just been 

 describing. Reverting to the graphic description of Mr. Miller, we 

 find it compared to the figure of a man rudely drawn, the head cut 

 off by the shoulders ; the arms spread out at full length as in the atti- 

 tude of swimming ; the body rather long than otherwise, and narrow- 

 ing from the chest downwards; one of the legs cut away at the hip- 

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

 under the centre of the figure, which it seems to support Something 

 of this appearance i indeed pmvnted in the fossil remains of these 

 creatures, once the tenants of the sea in our own latitude ; but we 

 are now able to describe with more minuteness, if not so vividly, the 

 real nature of the animal It was of small size, not more than a few 

 inches or a foot in length ; its head and body were defended by strong 

 plates of bone, coated with enamel ; and iU shape and proportions 

 were singularly unlike those of ordinary fishes, the head being small, 

 and the body much flattened but swelling out immediately at the 

 junction of the head and neck, and gradually tapering thence towards 

 the tail. From the junction of the head and body there extended 

 that pair of ningular paddles, or wings, from which the genus ha* 

 been named, and which have been supposed to answer the same pur- 

 pone as the horns of the crescent-shaped shield of the Crphatatpit, 

 and to defend the animal from the attacks of its soft-mouthed enemies. 



Besides those paddles, which were hard and pointed, and nearly as 

 long as the body, at least some species of Plcrichthyi seem to have 

 been provided with another smaller pair extending from the part 

 where the body is attached to the tail ; and it is thought that this 

 second pair of wing* may be the remains of anal fins, the other pair 

 representing the pectoral fins. The body, like the head, was certainly 

 covered on the upper side by hard plates, accurately fitting one 

 another, but the lower part both of the head and body was probably 

 defended by tough skin, capable of distension, and enabling the crea- 

 ture to swallow prey of large size. The position of the mouth is not 

 known with certainty, but it may have been formed by a transverse 

 slit, covered by thick fleshy lips, situated round the edge of the plate 

 which defended the head ; this position, and the absence of teeth, 

 readily accounting for the difficulty there is in discovering remains of 

 it in imperfect specimens. The eyes and the apertures of the nostrils 

 were probably extremely small, and placed on the edge of the broad 

 plate, the only indication of the head hitherto met with. The tail 

 was not long, but seems to have been thick and conical, and covered 

 with scales overlapping each other like the tiles on the roof of a 

 house. 



" The departure from the general form of most fishes in this 

 animal is so remarkable, that, when first discovered, it was looked 

 upon by some naturalists as an insect, by others as a crustacean, and 

 by others again it was thought to be connected with reptiles, owing 

 to the singular resemblance of one small species to the shell of a 

 tortoise. Strange as it undoubtedly is however in all respects, this 

 genus forms one of an extinct family of fishes, and it is allied to the 

 other genera of its class by the genus Coccottetu, which at one time 

 was thought still more anomalous. The Coccoiteiu is entirely with 

 out the wing-like projections which characterise the Pttrichthyt, and 

 while when seen, as in ordinary specimens, lying on its back and crushed, 

 it appears to bear no resemblance to any fish or other animal, 

 recent or extinct; it was not in reality much unlike many well-known 

 fishes in its general outline, although so oddly coated with large broad 

 plates, which were studded with enamel instead of scales. 



" The head of the Coccotteui was large, broad, and high, nearly cir- 

 cular in shape, covered by several plates, and attached to the body by 

 a very small articulating surface, resembling in this the insects, and 

 departing widely from the fishes. The jaws are large in proportion, 

 and armed with very strong pointed teeth ; the mouth opened as in 

 the cod and other well-known fishes, and no doubt rendered the 

 animal sufficiently formidable ; and the lower part of the head seems 

 to have been covered with a tough membrane capable of distension, 

 and enabling the animal to swallow very large bodies ; the upper part 

 of the body was chiefly covered by one large plate, and the lower 

 part by four plates of rather curious shape. The tail was large, and 

 much longer than the body, and was provided with two small fins. 

 The detached plates, more especially those which covered the body, 

 are frequently found fossil in certain localities of the Old Red-Sand- 

 stone. The fishes just described form together one of several groups 

 characteristic of the period we are now considering. But another 

 group also, containing four genera, is worthy of notice, as contrasting 

 strongly with the Cephalatpidet (as the former are called), and instead 

 of being clothed with large plates, these are recognised by the 

 extremely minute scales with which the fish belonging to it are 

 covered. These scales give to the skin an appearance very strikingly 

 resembling shagreen. 



" The size of the fishes thus brought together is generally small, 

 and their shape is squat and awkward, the head being large, and the 

 body dwindling away to a very small tail They have however largo 

 teeth, and must have been powerful if not very rapid fishes. Their 

 fins offer some peculiarities, being formed of a multitude of delicate- 

 jointed rays, generally terminated by one very powerful ray or spine, 

 sometimes simply planted in the flesh, sometimes articulated to bone. 

 Both this group and the former are entirely confined to the first 

 epoch, and almost entirely to the particular period of the Old Red- 

 Sandstone. 



" Another group of these ancient fishes (Dipterians) is remarkable 

 for the great magnitude to which the fins were developed, and the 

 fact that in all of them the fins on the back and below the tail are 

 double. The jaws of these animals were provided with sharp pointed 

 teeth ; the head inclosed as if in a box of cartilage coated with enamel, 

 and the scales of the body are in some species so large as not to have 

 required more than half a dozen to reach from head to tail. This 

 however was by no means a general character ; and the presence of 

 prominent spines supporting and defending the fins is probably more 

 essential It is probable that almost, if not all, the fishes of this 

 family of Dipterians were more rapid swimmers and more voracious 

 than those of the former two families. They are all however of small 

 size. Besides these there is another family, chiefly developed in tho 

 latter part of the period, and attaining a larger size. One of the 

 members of this group has been named Jfoloptychiut, and is confined 

 to the Devonian period. Its head was small compared with the size 

 of the body, whose proportions were so robust, and its covering of 

 large, rounded, deeply-wrinkled scales, on so grand a scale as almost 

 to deserve being called gigantic. The actual measurement of the body 

 in one complete specimen is 30 inches by upwards of 12 inches. The 

 jaws wore of bone coated with naked enamel ; a row of thickly-net 



