Dec. 1, 1870.] 



HARDWICKE'S SCIENCE-GOSSIP. 



267 



of fish known to naturalists the Ganoid species only 

 number about twenty-seven. Indeed, the wide 

 geographical areas where the two outliers of this 

 once numerous and world-wide family of fishes are 

 now lingering, indicate their antiquity, and suggest 

 how many geological phenomena have taken place 

 to bring about their present geographical isola- 

 tion. Eew of these peculiar species have a solid 

 skeleton properly hardened, as is the case with 

 ordinary thin-scaled fishes. No doubt the strong, 

 bony integument did duty instead. Indeed, among 

 the fish which lived during my lifetime, scarcely 

 any possessed a solid skeleton. The largest of 

 these strange-looking fish is now called Asterolepis, 

 from the star-like markings on each of the scales. 

 It reached the entire length of between twenty 

 and thirty feet. Other common forms were the 

 HoloptycJiiiis, noted for its large oval scales being 

 peculiarly wrinkled ; the Pterichthys, or " winged 

 fish," so called on account of its two pectoral fins, 

 which are very large and resemble paddles, being 

 placed near the head, where they look like wing 

 appendages. The plates which covered this fish 

 were very large, and ornamented by a series of 

 granules. 



Then came the Cephalaspis, or " buckler-headed " 

 fish, so called because its queer-shaped head was en- 

 cased in a shiny bony buckler, in form not unlike a 

 cheesemonger's knife. Its trilobed body was covered 

 with lozenge-shaped bony plates. The Osteolepis, 

 or " bony-plated " fish, was the most abundant ; its 

 name being derived from the minute rhomboidal 

 plates which covered its- body, and protected it, 

 like the links of an ancient coat of mail. Besides 

 the fishes of this class, which, singularly enough, 

 were further distinguished by their having the 

 tail unequally lobed — and not regularly cleft as 

 in the common herring and other scaled fishes — 

 there were associated with them others, having 

 an affinity with species of the Shark family. These 

 are called placoid fishes, on account of the skin 

 being a kind of shagreen, dotted with minute 

 plates or points of hard bony matter. They also 

 have a cartilaginous skeleton, as, for instance, the 

 common skate, sturgeon, &c. "Well do I remember 

 these peculiar fish, ranging in size from the Astero- 

 lepis to the little Onchus and Osteolepis, of only a 

 few inches in length ! The quick, active move- 

 ments of the latter, as they roamed in and out of 

 the thickest of sea-weeds, caused the light to flash 

 from their enamelled scales, and sometimes only 

 too surely pointed out their playgrounds to their 

 cestraciant enemies. They had their feeding and 

 their spawning-grounds, and each of these places 

 is now represented by the greater number of fish 

 found fossilized in the flagstones, as in the Caithness 

 flags, and the yellow sandstones of Dura Den. 



Sometimes, also, great numbers were killed by 

 unusual quantities of mud being poured into the 



water and choking them, as a turbid river will, at 

 the present time, suffocate the smaller of its tribes. 

 How suddenly these died is indicated by the fact that 

 thousands of fossil specimens are to be seen with 

 their fins erect, like those of the perch when he is 

 "struck." Others are contorted and bent, as if in 

 pain ; their last dying struggles having thus been 

 faithfully handed down by the stony records in 

 which they were imbedded. 



Some few of the fossil fish of this period had 

 reptilian characters in their teeth, &c, indicating, 

 as it were, the next great family which should rule 

 creation. Wherever the Old Red Sandstone has 

 been met with, some, if not all, of these peculiar 

 ganoid fishes have been found fossilized. Therefore, 

 they are good indications of the geological age of 

 any such formation. 



I will not trouble my listeners with the dry, 

 technical details of how the strata succeed each 

 other in my parent formation. I want, if possible, 

 briefly but vigorously to sketch the life-character- 

 istics of that distant epoch. 



I have thus far devoted myself to the fossil fishes, 

 because of their abundance, and also of their very 

 striking peculiarities. Now I come to other crea- 

 tures, perhaps not less abundant, but not so attrac- 

 tive. I must premise, however, that such marine 

 creatures as corals, mollusca, and trilobites were 

 not very abundant over the area where I first saw 

 the light. They delighted in clearer water, and so 

 are to be found over the area where that stood. 

 Indeed, generally speaking, those parts of the sea- 

 bottom where most of the red muddy matter was 

 poured in, were shunned by all forms of life, not 

 excluding the hardier fishes. Hence it is you rarely 

 find, in the very red sandstones, any organic re- 

 mains or fossils beyond a few vegetable impressions. 

 Of course there were various parts of the same sea 

 thus distinguished by different physical circum- 

 stances, and life was developed, or located, accord- 

 ingly. Let me, therefore, give you some slight 

 account of the area where " blue water " was most 

 in force, and where, in consequence, there were the 

 most numerous assemblages of Crustacea, shell-fish, 

 and corals. 



The localities in Great Britain where these 

 peculiar fossils are found in strata of the age I am 

 describing, lie chiefly in South Devonshire, as well 

 as along the North Devon coast. At the latter 

 place you may see beds of sandstone, red and yel- 

 low, alternating with slates, limestone bands, &c, 

 the last-mentioned being especially full of organic 

 remains. 



The highest of the series go by the name of 

 the " Pilton Group," and these are undoubtedly of 

 the same geological age as the Devonian strata in 

 Ireland. Among the fossil shells which lived during 

 this epoch, and Avhich occur at the above-mentioned 

 places in the fossil state, the most numerous were 



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