42 Fossil Fishes. 



the symmetrical caudal fin are those which are here found ; and among 

 the Placoides, it is especially those with teeth furrowed on their two 

 faces, and with large spinous rays, which predominate. For it is now 

 certain that those great rays which Dr. Buckland and M. de la Beche 

 have denominated Ichthyodorulithes belong neither to the Silures 

 nor to the Balistes, but are the rays of the dorsal fin of the great 

 Squali, the teeth of which are found in the same beds. 



" In quitting the Lias, and proceeding to the lower formations, a 

 great difference is observed in the form of the posterior extremity of 

 the body of the Ganoi'des. All of them have the vertebral column 

 at its extremity prolonged into an imperfect lobe, which reaches to 

 the extremity of the caudal fin, and this peculiarity extends to the 

 most ancient fishes. Another observation, which is worthy of remark, 

 is, that down to the coal formation, no fishes that are evidently car- 

 nivorous are found ; that is to say, with large conical and sharp teeth. 

 The others appear to have been omnivorous, their teeth being roun- 

 ded, or obtusely conical, or pencil-shaped. 



" The day is assuredly not far distant when we shall be able to 

 collect a great number of facts respecting the habits of these animals, 

 and their interior organization. The discovery of coprolites already 

 enables us to discover the organized beings which preyed upon the pi- 

 rates of the ocean ; for in these coprolites, which are sufficiently nu- 

 merous in those deposits which contain Sauroid fishes, we easily dis- 

 cover the scales of the fishes which they ate, and sometimes we can 

 determine the scales. Their intestines even are preserved in some 

 cases, as for an example in a specimen of Megalichthys, where a 

 portion of intestine is visible ; and bundles of pyloric appendices, and 

 the cul-de-sacs of intestines of the species Leptolepis and Thrissops 

 of Solenhofen, known by the name of Lumbricaria, are not rare in 

 the schists of this interesting locality. In the fishes of the chalk group, 

 there may be seen, in Dr. Mantell's collection, specimens of Mac- 

 ropoma, in which the whole stomach is preserved with its different 

 membranes, which are separated, as it were, into as many leaves. 

 In a great number of the fishes of Sheppey, of the chalk and oolite 

 series, the capsule of the eye-ball is still preserved ; and in many 

 species of Monte-Bolca, of Solenhofen, and of Lias, there are very 

 distinctly to be seen all the little laminae which form the gills. It 

 also appears evident that the constitution of some rocks is much more 

 favorable for the preservation of animal remains than that of others. 



