COMMON STURGEON. 161 



and more separate over the snout; and in all cases, as well 

 of the head as body, their surface is rough with radiated 

 lines. The eye is small, and sunk into a well-guarded cavity, 

 but is probably capable of protrusion. The nostrils are large, 

 in front of the eyes, and have a single cavity within, of which 

 the bottom is formed of a full circle of separate bony rays, 

 proceeding from a centre. On the surface it is crossed by a 

 membranous band, which gives the nostril the appearance of 

 being double, as in most bony fishes, but I could not discern 

 any membranous division within. The mouth is fleshy, re- 

 tractile, and seems not capable, except by living action, of 

 being closed. Teeth none. Bones of the jaws slight, the lips 

 with lobes, which probably have a quick feeling of touch and 

 taste. In front of the mouth, and rather nearer the snout 

 than it, are two pairs of tendrils, of considerable length. A 

 small spiracle behind the eye, between the border of the 

 anterior gill-cover and the j)lates of the head. The hinder 

 gill-cover, which is much the largest, being formed of a single 

 jilate, with radiating lines, appears fallen in and incapable of 

 concealing the gills, the more especially as these gill-covers do 

 not possess a membranous border. 



The body is lengthened. The dorsal and lateral ridges, 

 which are five in number, are so prominent that the surface 

 appears flaccid between them, the surface being soft and flexible, 

 with numerous pores. The dorsal row of plates, of which the 

 summits are not incurved, consist of fourteen, there being an 

 interruption in the line, where the place of one is represented 

 by a pair. The first rays of the dorsal fin are also armed 

 with plates along their edge; between that fin and the tail 

 there is a double jDarallel row, the edge of the caudal fin 

 being also guarded by pointed plates. Number of plates on 

 the side thirty, on the border of the beliy ten, reaching to 

 the ventral fins. Pectoral fins wide, with the first ray stout, 

 seeming to admit of motion easily forward and backward, but 

 not freely above or below. The ventral fins are far behind, 

 but anterior to the vent; the dorsal and anal hook-shaped, and 

 not far from the tail. The upper lobe of the caudal fin is 

 lengthened, and the vertebra?, as in the Sharks, carried along 

 to near its edge, but there is no slit to separate the upper 

 lobe from that below. The rays of this fin differ from those 

 VOL. I. 2 A 



