380 THE FRESH-WATER FISHES OF EUROPE. 



squamosal. These are the frontal shields. They are not in contact in the 

 middle line, because a number of small plates come between them, and extend 

 backward between the anterior ends of the parietal shields. These small ossi- 

 fications, of which there may be about eight, represent the ethmoid bone, which 

 in birds often occupies a large area anterior to the frontal bones. External 

 to the frontal plate, and coming above and behind the eye, so as to abut against 

 the squamosal, is the long post- frontal shield. At the anterior margin of the 

 frontal, above the nares, is the pre-frontal shield, and there is a small nasal 

 scute near the nasal margin. 



There are a few other scutes in front, extending to the extremity of the 

 snout, which would be regarded as pre-maxillary and maxillary plates, if it 

 were not that the jaws are far removed from the extremity of the rostrum, so 

 that they must probably be regarded as distinct in origin from the bony element 

 so named in the skulls of other vertebrates. Behind the epiotic, there are 

 shields which connect the back of the skull with the pectoral arch. The under 

 side of the head is naked, but the skin is in places rough with ridges, though 

 in front of the gill -opening the throat is defended with one long shield on each 

 side. The continuity of the armour of the head is broken only by numerous 

 large pores, which open through the soft skin, and run in the usual directions 

 of the cephalic canals, and give off similar branches to the hinder part of 

 the head, and the supra-orbital and infra-orbital areas. The latter branches 

 run to the end of the snout ; but numerous pores, irregularly placed, extend 

 beyond them, and cover the entire under surface of the head, as far back as the 

 upper lip (Fig. 176). The eyes are small, a little elongated, and protected by a 

 strong projecting, scutal margin. They are nearer to the end of the snout than 

 to the mouth. The breadth of the frontal interspace between them is equal to 

 six and a half times the orbital diameter. The nares are oval, and small,- but 

 the lower aperture is larger than the upper one. The barbels, which are 

 nearer to the snout than to the mouth, are rather long, and reach back nearly 

 to the upper lip. They are round at their bases, are rather compressed for half 

 their length, and thence are distantly fringed. The lips form a thick cushion 

 round the wide mouth ; they are deeply notched in the middle, but not 

 divided. 



The body is a little higher than wide ; and its diameter is one-eighth of 

 the total length. All the shields of the five longitudinal rows upon it, are 

 rather distant from each other. Only the scutes of the median dorsal row are 

 well developed ; the rows on the sides are small, and those on the ventral 

 margins are very small. The number of dorsal shields varies from twelve to 

 sixteen. The first dorsal shield is largest and highest, and the remainder of 

 the dorsal series gradually decrease in size. Except the last, which is lozenge- 



