COMMOM STURGEON. 
161 
and more separate over tlie 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 lohes, which probably have a quick feeling of touch and 
taste. In fr'ont of the mouth, and rather nearer the snout 
than it, are two pairs of tendrils, of considerable length. A 
small spiracle belfrnd the eye, between the border of the 
anterior gill-cover and the plates of the head. The hinder 
gill-cover, which is much the largest, being formed of a single 
plate, 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 
a23pcars flaccid between them, the surface being soft and flexible, 
with numerous jjores. 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 parallel 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 belly 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-shajied, and 
not far from the tail. The upper lobe of the caudal fin is 
lengthened, and the vertebrae, 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 
