442 



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 {L. 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 peculiarities of the skeleton is that the vertebrae instead of hav- 

 ing cup-like surface? as in the Amia and the ordinary bony fishes are united by a 

 ball and so3ket joint, the socket being on the hinder surface of each vertebra. 



The remaining representiveof this important grou^, ATnia 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 dermil 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 Mudfish is dark olive-green above, pale below, 

 but the males are marked by a round 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 Teleo>t^ in 

 which the air-bladder is closed are regarded as further removed from the Bony 

 Ganoids than the others, and it is therefore 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 is 

 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 difiers in being some- 

 what slenderer and in having the lower jaw projecting beyond the upper, and 



