Recherches sur les Poissons Fossiles. 



81 



are perfectly well preserved, and visible between the branchiostegous 

 rays and the orbit. It is impossible to recognize in the structure of 

 the branchial rays, the least difference from the pectinated branchies 

 of ordinary fishes of our own epoch. The orbit is surrounded by 

 the sub-orbital plates. Almost all the bones of the cranium are lost ; 

 but we find in front a fragment of the ethmoid, and of the anterior 

 frontal, the surface of which as well as that of the super- occipital 

 plates presents little round tubercles with supef-ficial openings, to the 

 number of four, which allow of our ascertaining the form and dimen- 

 sions of the head. In other specimens, says M. Agassiz, I found 

 that all the bones of the cranium, and particularly the opercular 

 pieces, present very close tubercular granulations. 



The only part of the trunk which presents the external surface 

 complete, is towards the tail ; along the dorsal and the anal we 

 see a small space where the solid parts of the body have entirely 

 disappeared, and have not left their impression. The scales are 

 very small along the back, and on the sides of the tail ; those of 

 the flanks are much larger, and particularly much higher than broad, 

 except towards the breast and under the pectorals, where they are 

 almost equilateral. Their surfaces are interspersed with irregular 

 asperities, almost like little round tubercles disposed in irregular 

 slightly raised lines. All their sides are straight, and their articu- 

 lating claws strong. 



The dorsal commences rather before the middle of the back, and 

 terminates at a distance from the caudal, equal to the base of the 

 caudal. The anal is large and short, and extends nearly to half the 

 length of the dorsal, but these two fins terminate opposite to each 

 other. The fin rays are slender, bifurcated only at the extremity, and 

 their articulations transverse, and very close ; at the anterior extre- 

 mity, there is a series of little fulcra, very close. The ventrals which 

 are very small, are placed opposite to the anterior border of the 

 dorsal. The pectorals, also small, have the rays proportionally slen- 

 der. The caudal is of middling length for the size of the fish, its 

 insertion is slightly oblique, because the rays of the inferior lobe are 

 inserted at the extremity of the spinous apophyses, which is extended 

 less behind than the base of the rays of the superior lobe. All the 

 fin rays are more slender in proportion in this^ than most other species 



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