338 



Recherches sur les Poissons Fossiles. 



nity to make myself acquainted with the species, (in general very badly 

 preserved), to enable me to trace their organization throughout all the 

 geological formations, in a manner so complete as the order of Ganoids, 

 I have therefore commenced with this division, whose species belong to 

 the coal formation. 



Scales angular, rhomboidal or polygonal, formed of os- 

 seous or horny laminae, covered with enamel. 



The families are the Lepidoids, the Lauroids, the Pycno- 

 donts, the Scleroderms, the Gymnodonts, the Lophobranchs, 

 etc. etc. 



1st. Family. — LEPIDOIDES, Agass. (Lepidostei, Agass.) 



Teeth crowded (en brosse) in many rows or one only 

 range of little obtuse teeth. Scales flat, rhomboidal 

 parallel to the body, which is all covered. Skeleton 

 bony. 



A. Body elongated, fusiform ; superior lobe to the caudal 

 vertebrae longer than the inferior,* all the teeth crowded 

 The genera are, Acanthodes, Catopterus, Amblypterus, Pa 

 IceoniscuS) t. xii. f. 1. and Osteolepis. 



B. Body flat, and large : 



1st. Superior lobe to the caudal vertebrae. The genera 

 are, Platysomus, and Gyrolepis. 



2d. Tail regular : the genera are Teragonolepis, Dapedius 



C. Body elongated, fusiform ; tail forked or round ; genera 

 are, Semionotus, Lcpidotus, Pholidophorus, Microps, and 

 Noiagogus. 



* This gives the peculiar obliquity to the base of the caudal fin 

 observed in figs. 1 and 2, plate 12. M. Agassiz has observed that this 

 obliquity depending on the proportional development of the upper 

 and under appohyses of the vertebrae, is confined to the fossil fishes 

 of the coal formation. Those species in which the obliquity is mos 

 prominent, have lived at the most remote period of the coal formation 

 and from thence the peculiarity gradually diminishes as we ascend i 

 the series of strata up to the chalk formation, where it is no longe 

 observed in the fossil fishes of that period. — Ed. 



