FISHES OP LAEE SUPERIOR. 279 



to settle this question is plain, as soon as we consider the position of 

 those fins in the Ganoids, in which they are also placed at the middle of 

 the abdomen. The scales which are wanting in most Siluridge, would 

 apparently seem, at first sight, to afibrd little information ; let us how- 

 ever remember that there are some genera among Siluridge, such as 

 Callichthys and Doras, in which scales of a very peculiar character 

 exist, and that several other genera have large bony escutcheons 

 upon their neck. Now these bony plates and scales have the same 

 structure as the enameled scales of the sturgeons, and their position 

 in Doras reminds us strongly of the lateral shields of sturgeons ; so 

 much so, that but for the form of the body, we might be led to con- 

 sider these fishes as closely related. And really, this affinity is not 

 altogether superficial ; the development of the jaws and opercular 

 bones is so imperfect, as to show little analogy to the structui'e of 

 those parts in the common Abdominales, whilst it agrees rather closely 

 to that of the sturgeons. The position of the mouth in Ldricaria, 

 below the snout, is another feature which connects the Goniodonts 

 and sturgeons, and the genus Scaphirhynchus may be considered as 

 forming the most natural link between the two families. Again, 

 Goniodonts have pseudobranchise and a thick membrane encircling 

 the mouth, which constitute so many more characters connecting them 

 with the sturgeons ; although these points are of less value than those 

 already mentioned. I may add, also, that the brain of Siluridre bears 

 a stronger resemblance to that of the sturgeons, than to that of any 

 of the Abdominales ; so that I consider myself justified in referring 

 the families of Goniodonts and Siluridae to the order of Ganoids, 

 where they may stand as aberrant famiUes, rather than among the 

 other great divisions of the class of fishes. 



PiMELODUS. 



The genus Pimelodus, as characterized by Prof. Valenciennes, in 

 the Histoire Naturelle des Poissons, seems to me to contain several 

 distinct types, which might with great propriety be considered as 

 distinct genera, characterized by their peculiar teeth, the arrange- 

 ment of their barbels, and the respective position and extent of their 

 dorsal and anal fins, as well as the form of their caudal. But as the 



