134 



NORTHERN ZOOLOGY. 



it, at one corner, thus supplying the place of the suboperculum, which is wanting in this genus : 

 the preoperculum, though firmly connected to the operculum by bone, is marked out by its 

 slightly-elevated edge, but the interoperculum cannot be traced through the skin. There are 

 nine gill-rays, all cylindrical except the two superior ones, which are flattened at their upper 

 extremities. The gill-openings are rather confined. The humeral bones are strong and 

 spreading, with a process which can be felt through the skin, extending backwards above the 

 pectoral ; the nape is smooth. 



Fins.— Br. 9; D. 1/7—0; P. 1/8; V. 8; A. 24; C. 17&. 



The dorsal contains seven branched rays, the first of which is sheathed in the deep posterior 

 groove of a strong acute pointed bone, that can be erected or depressed at the will of the fish. 

 This bony spine is a little shorter than the first soft ray. The adipose fin corresponds to the 

 hinder part of the anal. The pectoral is armed still more strongly than the dorsal, by a 

 bone which is triangular at the base and compressed towards its acute tip : its posterior edge 

 is serrated by ten or eleven acute teeth pointing downwards. The ventrals are posterior to 

 the dorsal, and a little nearer to the caudal fin than to the end of the snout. The anal 

 and caudal are large, and their outline, like that of the dorsal, is slightly rounded : the former 

 has twenty-four rays, including three short anterior ones, and the caudal has many short basal 

 ones, with seventeen long ones. 







Dimensions. 











Inches. 



Lines. 







Inches. 



Liues 



:ngth from end of snout to tips of central 







Length 



of adipose fin . 



. 



7 



caudal rays ..... 



10 



4 



» 



pectoral spine 



1 







„ „ centre of orbit 



1 



1 



» 



rays of pectoral . . 





a 



„ „ posterior angle of gill-cover 



2 



4 



j> 



ventrals 





l 



,, „ dorsal fin . 



3 



2£ 



j) 



attachment of anal . 





9 



,, „ ventrals . 



4 



8 



» 



its central rays 





2 



„ ,, anal .... 



6 







j' 



lateral caudal rays . 



1 



8J 



„ of attachment of dorsal 







9* 



t: 



its central rays 





6 



„ central rays of ditto 



1 



5 











„ dorsal spine 



1 















[59.] 2. Silurus (Pimelodus) nigrescens. (Le Sueur.) Black 



Pimelode. 



Pimelode noiratre (P. nigrescens). Le Sueur, Mem. Mus. d'Hist. Nat. Paris, v. p. 153, 

 PI. 16. Lowest figure. 



The black pimelode described, together with six other species, by M. Le Sueur, 

 in the work quoted above, inhabits Lakes Erie and Ontario and their tributary 

 rivers, frequenting places where the bottom is muddy. It is said to attain a great 

 size, and is a sluggish, inactive fish, generally lying still for a long time in one 



