11 



body is entirely naked, and the arrangement of the muscles is very ap- 

 parent. 



It is very doubtful whether this order truly belongs near to the preced- 

 ing orders, and it is only provisionally retained here. By Sir John Richard- 

 son, in the valuable essay on " Ichthyology," in the Encyclopaedia Brit- 

 annica, it is placed as a third suborder of the Dermopteri of Owen. Un- 

 til it is better known, we prefer to retain it among the Teleostei, to which, 

 notwithstanding the rudimentary condition of its organization, it appears 

 to be more nearly allied. Sir John Richardson referred it to the Derm- 

 opteri on account of the " absence of ossification in the skeleton, the 

 gelatinous condition of the sheath of the spinal marrow, which, in the form 

 of a ' chorda dorsalis,' reaches into the base of the skull, and the per- 

 sistence of the primordial cartilaginous cranium." 



A single species, the Leptocephalus gracilis of Storer, is found on our 

 coast. 



rder NEMA TO GNA THI Gill.* 



The body is either naked, or protected by ganoid plates. The branchiae 

 are pectinated and supported on four arches as in the Teleocephali. 

 The supra-maxillary bones are little developed, and are enveloped in the 

 integuments which terminate in longer or shorter barbels. The suboper- 

 cular bone is always absent. The rays are mostly articulated and 

 branched. 



This order embraces the "Catfishes," "Horn-pouts" and "Bull-heads" 

 or Idalurif of North America. It embraces five families, and about 

 one hundred and thirty or forty genera, which are chiefly represented 

 in Asia and South America. 



He has remarked on the general absence of sight in those animals found in 

 caves and localities from which the light is excluded, and concludes that the 

 want of that sense is of generic importance. While we are disposed to believe 

 in the validity of the genus established by him, we can scarcely coincide in 

 his views. The modification of a single organ dependant on the mode of life, 

 we cannot yet regard as by itself of generic importance. But in most cases, 

 such a modification is accompanied by others, and in conjunction with them, 

 it assumes a systematic value. 



These remarks have little relation to the subject in hand, but we have been 

 naturally, although unintentionally, led to them, and think it advisable to re- 

 tain them. 



*" Ichthyologise Archipelagi Indici Prodromus, auct. P. Bleeker, " vol. 1. 

 Siluri ; lb., in " Acta Societatis Scientiarum Indo Nederlandicae, " vol. iy. 

 1858, is a valuable monograph of the order. 



tRafinesque first named and well defined the group of freshwater "Cat- 

 fishes" of North America, conferring upon them the subgeneric name of Ictalu- 

 rus, and dividing that subgenus into sections, some of which are of generic 

 value. We admit four, Ictalurus ; Arniurus, of which the common catfishes of 

 the eastern streams are representatives ; Hopladelus, and Noturus. These 

 genera will be described and illustrated in the forthcoming report of Captain 

 Simpson, U. S. A. 



