278 LAKE SUPERIOR. 



Its head is thicker than it is long, forming one-seventh of the 

 whole length, which is twenty inches ; the snout is covered with dis- 

 tinct small plates upon its surface, though it is also granulated. The 

 frontal sinus is broader than deep, and extends over that part of the 

 snout which is contiguous to the skull. The dorsal plates, twelve or 

 thirteen in number, are elliptical ; the lateral series number twenty- 

 five or twenty-seven, and resemble somewhat those of the preceding 

 species. The abdominal series have eight or nine plates, longer 

 than broad, whilst the contrary is the case in the A. rliynchceus, from 

 the Sault St. Mary. Their circumference is also less. The fins 

 which we have been able to compare show but slight differences 

 in the two species. 



SlLURID^E. 



Whenever we are induced to consider organized beings in 

 their connection rather than by themselves, we perceive at once 

 differences between them, which throw more light upon the laws 

 that regulate their structure, than the most minute investigation of 

 isolated facts. The Siluridre are fishes which it is difficult to combine 

 with any other group, unless by far-fetched considerations, and afford 

 a striking example of the importance of general considerations in the 

 special study of zoology. 



Speaking of the sturgeons above, I have already mentioned their 

 affinity to the Goniodonts. It is now a matter of great importance to 

 examine upon what this relation rests, for the systematic position 

 assigned to that family is also decisive for the Siluridse, which are 

 very closely allied with the Goniodonts. Indeed, Goniodonts and 

 Siluridre may be united into one family with almost as much pro- 

 priety as they can be separated, and wherever one of these groups is 

 placed, in a general classification of fishes, the other must follow. 

 That sturgeons belong to the order of Ganoids is now fully ascer- 

 tained ; but whether the affinity of Goniodonts and sturgeons is suf- 

 ficient to connect the Siluridre, or whether Siluridse and Goniodonts 

 are to continue in some connection or other with the many fam- 

 ilies of Abdominales, with which they have hitherto been combined, 

 remains to be seen. That the position of the ventrals is not sufficient 



