364 LAKE SUPERIOR. 



of St. Mary. The species described before are about equally di- 

 vided between Europe and Syria. The principal character of the 

 genus is to have the mouth opening upwards, the lower jaw exceed- 

 ing a little the upper (PI. 3. figs. 2 and 3.) The dorsal is narrow ; 

 the anal slightly broader. The body is compressed. 



Alburnus rubellus, Agass. 

 PI. III., figs. 1-3. 



This is as yet the only species of the genus found in North America. 

 The body is compressed ; its form is elegant, slender, the back some- 

 what more convex than the belly ; the tail is contracted. The great- 

 est height of the body corresponds to the anterior third, or the region 

 situated between the pectorals and the ventrals, and is contained 

 six times in the length, exclusive of the caudal fin. The head, small, 

 conical and compressed, like the sides, is somewhat less than the 

 fifth of the whole length. The upper surface continues the declivous 

 line of the back towards the end of the snout. The eyes are large 

 and circular, approaching the upper region of the head, and at an 

 equal distance from the end of the snout and the posterior extremity 

 of the opercular apparatus. The suborbital ossicles are three in 

 number ; two are contiguous to the posterior and lower margin of 

 the orbit, the other at the anterior margin, covering the whole space 

 between the nostrils and the lower maxillary. The nostrils, propor- 

 tionally large also, are nearer to the eyes than to the extremity of 

 the snout, and opening into two apparently equal orifices. Fig. 2, 

 which represents the upper surface of the head, shows only the ante- 

 rior orifice, the posterior being covered by the intermediate mem- 

 brane which separates them from each other. The mouth is 

 moderately opened ; its angles reach behind a vertical line which 

 would pass before the eyes. The lower jaw slightly exceeds the 

 upper (figs. 2 and 3.) 



The preoperculum is rounded at its posterior margin. The lower 

 margin of the operculum is straight and oblique. The subopercu- 

 lum is narrow, and terminates behind in a point ; its upper margin, 

 contiguous to the operculum, is straight ; its lower margin forms a 

 slight elliptical curve. Scarcely can we distinguish the lower mar- 



