FISH OF ONTARIO. 



(i) Silver Lamprey. Lamper Eel. 



(Icthyomyzon concolor.) 



Body rather stout, compressed posteriorly. The head is broad and 

 the buccal disk large, with its edges not conspicuously fringed. The tooth 

 on the front of the tongue is divided into two parts by a median groove, 

 and the dorsal fin is continuous but deeply notched. The maxillary tooth 

 is bicuspid ; the teeth on the disk are in about four series and all small. 

 The tooth-bearing bone of the lower part of the mouth has seven cusps. 

 There are fifty-one muscular impressions from gills to vent. 



Colour bluish silvery, sometimes with blackish mottlings. Above each 

 gill opening there is a small bluish blotch. Length about twelve inches. 



The Silver Lamprey is abundant in the Great Lakes, usually in deep 

 water, but it runs up the small streams to spawn in the spring. It is a 

 most destructive parasite on the large commercial fishes, fixing itself to 

 their bodies by means of its suctorial disk and causing deep ulcerated 

 wounds at the point of attachment, which very frequently result in death. 



When spawning they form nests in the bed of the stream among 

 cobble stones and pebbles ; in these the eggs are deposited, after which 

 the parent fish all die. After emerging from the eggs the larvae burrow 

 in the mud or sand near the margin of the stream and there remain in 

 the larval condition, blind and toothless for a long period, sometimes until 

 they have attained a length of eight inches. 



GENUS LAMPETRA. 



Dorsal fin either notched or divided into two parts, the posterior part 

 continuous with the anal around the tail ; supraoral lamina broad, cres- 

 centic, with a large obtuse cusp at each end and sometimes a minute 

 median cusp ; lingual teeth small, with a crescentic toothed edge, the 

 median denticle enlarged; buccal disk small, with few teeth which are 

 never tricuspid. 



The genus Lampetra is best distinguished from Petromyzon by the 

 structure of its so-called maxillary tooth, which has the form of a crescent 

 shaped plate with terminal cusps and sometimes an additional median 

 cusp. In Petromyzon this bony plate is short and contains two or three 

 teeth which are very closely placed. 



