440 



raw sores by the aid of its rasp-like teeth. They ascend brooks in spring 

 to spawn, and it is probable that the young are at first toothless and blind, living 

 in sand until they attain a considerable size. Further information is desirable as 

 to this Lamprey from a scientific point of view, but it is of no economic import- 

 ance, whereas the Marine Lamprey, which attains a size of three feet, was for- 

 merly much valued as an article of food. It ascends rivers in the spring to 

 spawn and resembles, therefore, in this respect its representative in the lakes, 



Sub-Class IV. — The Ganoidei. 



This group embraces but few living forms — -most of them North American- — 

 but very many fossil representatives are known, so that the living species are 

 really only to be regarded as straggling survivors of a formerly numerous group. 



The name Ganoid is taken from the enamelled scales so well developed in 

 the bony pike. In many respects the structure is intermediate between that of 

 the Sharks on the one hand, and that of the Teleosts and Lung-fishes on the other. 



Two divisions of the group are recognized — the cartilaginous and the bony 

 Ganoids. Both are represented in Ontario, the one by the Sturgeons (family 

 Acipenserid.e), the other by the Bony Pikes or Gar Pikes (Lepidosteed.e) and 

 the Mud-fishes (Amiid.e). 



Of the various families the Sturgeons (Acipenseridcv) approach most 

 closely to the Sharks in their structure. Thus the skin possesses minuts bony 

 plates roughened with teeth which recall the shagreen of the Shark. The 

 skeleton is cartilaginous throughout, although the skull is encased by a series of 

 Hat bones formed from the skin, and similar in this respect to the bony shields 

 on the trunk. The latter are very characteristic for the family; they are in five 

 rows — a median dorsal series and a lateral and ventral series on each side — all 

 are keeled and provided with a spine. The snout or rostrum, which is of con- 

 siderable size in the allied paddle-fishes (Folj/odon) and shovel-nosed Sturgeons 

 (S(Xi2JhirJi,y7ichus) of the Mississippi Valley, is conical in form and carries in 

 front of the mouth, which is on the under surface, a row of four barbels. The 

 Sturgeons are bottom feeders, the position of the mouth and its protractile lips 

 are therefore very advantageous for this kind of life. The air-bladder is of large 

 size and has a wide opening into the gullet. 



The pectoral and ventral fins are situated low down, the latter far back, but 

 still in front of the dorsal and anal fins, which are similar in form and are 

 separated from the caudal fin by a slenderer part of the tail the " caudal peduncle." 

 The caudal fin is unequally divided by the continuation of the vertebral column, 

 and is distinctly " heterocercal." The gills are, however, much more like those 

 of the Teleost, consisting of a double row of gill-filaments attached to each of the 

 four gill-arches, and, in addition, of a single row attached to the hyoid arch, the 

 so-called opercular gill. The free edges of these look into the gill-chamber, 

 which is enclosed by an operculum, in which, however, only two of the four bones 

 usual in the Teleosts are found. There are no branchiostegal rays. Another 

 rudimentary gill (the pseudobranch) is situated within a rudimentary gill-slit 

 between the jaw and the hyoid arch, known as the " spiracle," and common in the 

 Sharks and Rays. Although the pseudobranch is frequently present in the 

 Teleosts, the spiracle itself is always absent, and it is hardly to be detected in the 

 other families of Ganoids referred to. 



The only member of the family occurring in the Province is the Lake 

 i^turgeon or Rock Sturgeon {Acipense7' ruhicundus). Like the other members of 

 the genus, this species attains a considerable size, up to six feet, and to a weight 



