Prof. Reid on the Vogmarus Islandicus. 459 
course of the bodies of the vertebre, and runs parallel to the mesial 
line of the bodies of the vertebre in that part of the body of the 
animal occupied by the anterior caudal vertebrz, but on proceed- 
ing backwards it tends a little downwards, so that for the last 9 
or 10 inches of its course it lies immediately below the lower edge 
of the bodies of the last caudal vertebre, and at its termination 
meets its fellow of the opposite side at the lower edge of the body. 
Opposite each vertebra this tissue is thickened, forming a series 
of small, irregular-shaped, slight elevations lying in the course 
of the lateral line, from the centre of each of which in the 
neighbourhood of the tail, but there only, there projected a 
small, hard, sharp spine curved forwards. Many of these ele- 
vations have a puckered or stellated appearance. When the 
colouring matter on the surface is rubbed off, the small tubercles 
on the surface of the chorion or true skin are brought more di- 
stinctly into view. These tubercles are small and placed near 
to each other. From nine to fifteen of them may be counted 
lying in, or nearly in, the same line in a space of an inch in 
length. They vary from ,%,ths to 54th of an inch in length in 
their longest diameters, and are very slightly elevated above the 
_ surface of the chorion. The largest are about j3,ths of an inch in 
length, and 2,ths in breadth. The larger are placed in parallel 
rows, a double row running in the course and nearly through 
the whole length of each interneural spine*, beginning at the 
upper edge of the body, and terminating opposite the part where 
the interneural spines dip downwards between the upper extre- 
mities of the spinous processes of the vertebre to be united 
to them by fibrous tissue. The smaller and much more nume- 
rous tubercles are about one half the size of the largest, are scat- 
tered irregularly in the intervals of the double rows and over the 
rest of the surface of the body. These tubercles differ in their 
intimate structure from those more prominent ones arranged 
along the lower edge in the manner to be afterwards described. 
As the varied relative heights, at different parts of the body, 
of the space between the lateral line and the lower margin of the 
body, that between the lateral line and the upper extremities of 
the spinous processes of the vertebre, and of that between the 
upper extremities of the spimous processes of the vertebra and 
the upper margin of the body or that occupied by that portion 
of the interneural spines placed above the upper extremities of 
* The term interneural spines applied by Professor Owen to the inter- 
spinous bones is used here, for the structure referred to is not in this fish 
composed of ossecus tissue as in the osseous fishes, but of cartilaginous and 
a peculiar tissue, and is in all respects so unlike bone, that I feel a great re- 
luctance to give them the name of bones. No doubt the term ‘ spine ’ is not 
an appropriate one either, but it is less incongruous than that of ‘bone,’ 
