SVR LES POISSONS FOSSILES DE l'aRGILE DE LONDRES. 301 



Denies le genre des Pentapodes qui comprend des especes a bouclie moins 

 fendue, a tete tres ecailleuse, et a caudale ecailleuse jusqu'au bout. C'est 

 £1 cote de ce genre qu'il faut placer notre Sciaenurus. Ce qui le distingue 

 c'est son corps comprime et eleve, tandis que les Pentapodes out le corps 

 fusiforme et allonge. II se distingue en outre par sa dentition ; les Dentes 

 ont comme les Pentapodes des dents inegales ; les Pentapodes ont deux 

 fortes canines qui surgissent entre plusieurs autres dents crocliues plus 

 petites placees en arriere entre des dents en velour ras. Le genre Sciae- 

 nurus n'a point de canines, ses dents diminuent d'une maniere egale d'a- 

 vant en arriere ; elles sont toutes crochues. Mais tout en se rapprochant 

 des Pentapodes par la caudale ecaillee a la base, il se place d'un autre 

 cote pres des Dentes par son corps comprime. Mon genre Sparnodus 

 dont j'ai decrit plusieurs especes de Monte Bolca, se rapproche aussi du 

 genre Scisenurus par I'uniformite de ses dents, mais il en differe en ce que 

 ses dents sont courtes et tres-obtuses. 



Je connais maintenant deux especes du genre Scisenurus, provenant toutes 

 deux de I'argile de Londres, de Sheppy. 



II faut etre sur ses gardes pour ne pas confondre avec les Sciaenurus les 

 fragmens d'une espece de Myripristis qui s'en rapproche beaucoup par sa 

 forme generale, mais qui en differe par les rides saillantes de I'opercule et 

 par la structure des ecailles. Ce n'est que par un examen tres-approfondi de 

 tous les exemplalres que j'ai eus a ma disposition que j'ai reussi a determiner 

 exactement ce genre ; mais il se pourrait bien qu'entre les echantillons que 

 j'ai etiquetes dans les collections d'Angleterre il se trouvat quelque fragment 

 de Myripristis sous le nom de Sciaenurus. 



Apres ces details venons-en a examiner les caracteres d'ensemble des 



bital which nearly hides the whole of the superior maxillary. Cuvier distin- 

 guished from the true Dentices the genus Pentapodes, which comprises the 

 species, having the mouth less divided, with very scaly head and caudal scaly 

 to the end. It is by the side of this genus that Scicenurus should be arranged ; 

 its compressed and raised body distinguishes it, while in the Pentapodes the 

 body is fusiform and elongated. It is moreover characterized by its dentition ; 

 the Dentices, like the Pentapodi, have the teeth unequal ; the Pentapodi have 

 two strong canines, which are situated between several other smaller hooked 

 teeth, placed behind the teeth en velour ras. The genus Scicenurus has no 

 canines ; its teeth diminish equally from the front hindwards ; they are all 

 hooked ; but while approaching the Pentapodi by the caudal which has scales 

 at the base, it is, on the other hand, related to the Dentices by its compressed 

 body. My genus Sparnodus, of which I have described several species from 

 Monte Bolca, likewise approaches to the genus Scicenurus, by the uniformity 

 of its teeth, but it differs from it in the teeth being short and very obtuse. 



I am at present acquainted with two species of the genus Scicenurus, both 

 derived from the London clay of Sheppey. 



It is necessary to guard against confounding the fragments of a species of 

 Myripristis with the Scicenuri, to which they approach considerably in their 

 general form, but differ from them by the prominent striae of the operculum, 

 and by the structure of the scales. It is only by a very minute examination 

 of all the specimens which I have had at my disposal, that I have succeeded 

 in accurately determining this genus ; it is however possible that among the 

 specimens which I labelled in the English collections, some fragment of Myri- 

 pristis may occur under the name of Scicenurus. 



After these details we will now examine the collective characters of the 



