24 The Ottawa Naturalist [May 



mann (1896, p. 9) for separating the two genra. For example, 

 Lampetra is said to have the extraoral teeth never tricuspid and yet 

 L. cibaria is described as having the middle tooth of each side usually 

 tricuspid. With their diagnosis of the genus this species is included. 



Ichthyomyzon bdellium (Jordan). Silvery Lamprey. 

 Syn. /. concolor. 

 St. Lawrence river below Quebec (Fortin,1864 as Petrotnyzon). 

 St. Lawrence river (Provancher, 1876, p. 262, as I. castaneus). 

 St. Lawrence river near Montreal (Huard, 1902, p. 169). 

 Go Home river, Georgian bay (Bensley, 1915, p. 9). 

 Brigham's Creek, Hull, Que., May 6, 1908, (coll. Canadian 



Fisheries Museum, Ottawa). 

 "North River, Ottawa" (coll. Peter Redpath Museum, McGill 



University). 

 Point Pelee, Lake Erie, 1913 (coll. Victoria Memorial Museum, 



Ottawa, No. 1012). 

 Lake St. Clair, 1882, from a pike (coll. Biological Department, 



University of Toronto). 

 Mitchell bay, Lake St. Clair, April '30, 1880 and 1883 (coll. 

 Biological Department, University of Toronto). 

 I have been unable to obtain any examples from the drainage area 

 of Lake Ontario. Its occurrence both in the St. Lawrence river and 

 its tributaries and in the upper lakes makes it fairly certain that it will 

 be found in the waters of Lake Ontario also. Much collecting has 

 been done, however, in the waters of northern New York State, yet I 

 know of no record of its occurrence there except at Cape Vincent on the 

 St. Lawrence (Evermann and Kendall, 1902b, p. 235). To the 

 northwest it has been reported from the Hayes (or Hill) river in 

 Manitoba (Evermann and Goldsborough, 1908, p. 90), which is not 

 far from the boundary of Ontario. It is probably generally distributed 

 throughout northern Ontario. 



Jordan and Evermann (1896, p. 10) state that the anterior lingual 

 lamina 'in Ichthyomyzon is divided by a median groove, whereas Regan 

 (1911, p, 199) gives it as "a single transverse denticulated ridge." In 

 a series of specimens, ranging from 9.2 to 37 cm. in length, in no case 

 is there an actual division of the lamina into two parts, but in all cases 

 there is a median groove (deeper in the larger specimens), which is 

 similar to that seen in Petromyzon marinus. In the latter, however, 

 the teeth on the lamina appear to be distinctly longer. The lingual 

 lamina would seem to be of no value in separating these genera. 



Characters, in the specimens at hand, that distinguish this species 

 are: 



Dorsal fin continuous, with a broad, shallow notch. 

 Supraoral lamina with from two to four cusps (two in all cases 

 except one, where there are four). 



