66 



Recherches sur les Poissons Fossiles. 



In descending from the lias to the lower formations, we 

 observe a great change in the posterior extremity of the 

 Ganoides. All have the vertebral column prolonged to the ex- 

 tremity of the caudal fin in an unequal lobe ; and this peculi- 

 arity belongs to all the more ancient fishes ; vide. fig. 1 page 77. 

 One other observation is worthy of remark, namely, that we 

 do not find carnivorous fishes, that is to say, fishes armed with 

 strong conical and sharp teeth, in beds anterior to the coal 

 formations. They rather appear to have been omnivorous, 

 their teeth being rounded, or in obtuse cones, or crowded, 

 ( en hrosse,) We may safely hope one day to be able to 

 collect a great number of facts, relative to the habits and 

 internal organization of these animals. The discovery of 

 Coprolites has already afforded an insight into the character 

 of the organic beings which afforded food to these pirates 

 of the ancient seas ; for in the Coprolites which are numerous 

 in the repositories of Sauroid fishes, we readily discover the 

 scales of the fishes which they devoured, and sometimes these 

 scales are determinable. Even the intestines are preserved, 

 as in the case for instance of a kind of Megalichthys, where 

 we see a portion of the intestine ; the bundle of pyloric ap- 

 pendices, and the ends of intestines of species of Leptolepis, 

 and of the Thrissops of Solenhosen, knovi^n under the name 

 of Lumbricaria, are not rare in the schists of this interesting 

 locality. In the fishes of the chalk, examples may be seen 

 in the collection of Mr. Mantel where the entire stomach is 

 preserved, with the different membranes by which it is sepa- 

 rated into coats. In a great number of fishes of the chalk, 

 of the isle of Sheppy, and of the oolitic series, the capsule of 

 the eye ball is still entire ; and in many species of Monte- 

 Bolca, of Solenhosen, and of the lias, we see very distinctly 

 all the little laminae which constitute the branchas (or gills). 

 It appears however that the peculiar nature of parti- 

 cular rocks, contribute to preserve some parts rather than 

 others. 



