442 
a 
obliquely arranged lozenge-shaped scales which are so characteristic of the genus. 
The jaws are elongated into a beak which is twice the length of the head in the 
long-nosed species (LZ. osseus), but shorter and oroader in the other species. In 
both the beak is very well provided with teeth, there being several rows of small 
teeth and one row of larger size. . 
As in the Sturgeon, there is a hyoidean half-gill attached to the deep surface 
of the gill-cover, but the spiracles do not open to the outside and are small in 
size. One of the peculisrities of the skeleton is that the vertebrae instead of hav- 
ing cup-like surfaces as in the Amica and the ordinary bony fishes are united by a — 
ball and socket joint, the socket being on the hinder surface of each vertebra. 
The remaining representiveof this important group, Amia calva, is of common 
occurrence in the Great Lakes and sluggish waters southwards. In various 
places it is known under different popular names:—Lake Dogfish from its 
voracity, Mudfish from the waters it frequents, Bowfin from the characteristic 
long dorsal. In shape the Mudfish somewhat recalls the Shad tribe, and it is 
perhaps to this division of the bony fishes to which it is most nearly allied. All 
naturalists are agreed that the Amia is the leading representative of an extinct 
transition group between the ancient Ganoid fishes and the modern Teleosts. 
From the latter, however, there are still many points of distinction ; such as 
the completeness of the cartilaginous skull under the outside dermal bones encas- 
ing it, the presence of a similar dermal bone between the lower jaws and of two 
peculiar file-like structures attached to the hinder edge of the gill-opening. 
The general colouring of the Mudtish is dark olive-green above, pale below, 
but the males are marked by around black spot bordered by yellow at the base of 
the caudal, which is absent in the females. 
SuB-CLASS V.—TELEOSTEI. 
The general structure of the Teleosts has been described on p. 429; 
it now remains to give some details as to the peculiarities of the various sub- 
divisions of the group. 
They are primarily classified into Physostomous and Physoclystous 
Teleosts :—i.e. those in which the air-bladder opens into the gullet in the adult, 
and those where it is completely shut off. Even in those forms where the air- 
bladder does open by a tube into the gullet, its importance as a breathing organ 
is quite unlike that in the Bony Ganoids, and its functions are therefore regarded 
as being more closely related to the locomotion of the fish. Those Teleosts in 
which the air-bladder is closed are regarded as further removed from the Bony 
Ganoids than the others, and it is theref ore desirable to treat of the latter first 
PHYSOSTOMI, 
In this division the scales are usually cycloid, and the fin-rays (with the 
exception of one or more anterior ones, modified into defensive spines) soft. 
The most primitive families are undoubtedly the Catfishes, Suckers and 
Minnows, and they all agree in possessing the connection between the air-bladder 
and the ear referred to at p. 434, besides other anatomical features which it 1s 
impossible to describe. 
A sufficient account has been given above of the structure of a typical 
representative of the family SILURID#, and it only remains to make a brief refer- 
-ence to the other species of the family that occur in Ontario. | 
In addition to the ordinary Catfish (Amiurus nebulosus), two other 
species occur within the Province—A. vulgaris, which differs in being some- 
what slenderer and in having the lower jaw projecting beyond the upper, and 
