1917] The Ottawa Naturalist. 25 



Infraoral lamina with from five to nine cusps (5, 6, 6, 7, 7, 7, 



8,8,8,8,9,9). 

 Lateral teeth all unicuspid (one specimen, 17.5 cm. long of 

 doubtful origin has one bicuspid tooth on the left side and 

 three on the right). 

 18 to 21 complete radial rows of teeth, counted on side next 

 mouth (18, 18, 18, 19, 20, 20, 20, 20, 20, 20, 21, 21). 

 The new species, /. fossor, described by Reighard and Cummins 

 (1916) from Michigan, differs in a large number of points from this 

 species. The most striking thing is the degeneration of the dentition, 

 the radial rows being incomplete peripherally. There is at the same 

 time an increase in the number of cusps on the infraoral lamina (8 to 

 10) and in the number of the radial rows (28 in the specimen figured). 

 The latter character is to be found also in Entosphenus wilderi, which 

 has a still further reduction in the dentition. 



Forbes and Richardson (1908, p. 9) consider that the western 

 form (/. castaneus) is not distinct from this. Illinois appears to be 

 in the transition region between the two forms, which are evidently 

 only geographical varieties. Somewhat over half of their specimens 

 had bicuspid extraoral teeth. 



Regan (1911, p. 199) has rightly restored Jordan's name 

 {bdellium) for this species. Kirtland's name (concolor), under which 

 this species has ordinarily gone, was based on a larva which may or 

 may not have belonged to this species. 



Petromyzon marinus L. Sea Lamprey. 



This form is found on the coasts of the lower provinces and enters 

 their rivers. 



"Saint-Joseph de Levis," Quebec (Roy, 1906, p. 33). 



Petromyzon marinus, var. dorsatus Wilder. Land-locked Sea 

 Lamprey. 



Syn. Petromyzon marinus unicolor. 



Great Lakes (Wright, 1892, p. 439 as P. concolor). 



Great Lakes (Nash, 1908, p. 9 as Ichthyomyzon concolor). 



Lake Ontario (Nash, 1913, p. 249 as /. concolor). 



Lake Ontario (Bensley, 1915, p. 10). 



Port Credit, Lake Ontario (coll. A. R. Cooper). 



Lake Ontario (coll. Provincial Museum). 

 This form has for Canada been reported definitely only for Lake 

 Ontario. Bensley suggests that a large lamprey reported by fishermen 

 from the upper lakes may prove to be this species. Wright's figure 

 of the oral hood is definitely referable to this species, which was con- 

 fused with Ichthyomyzon bdellium. The latter had been found in 

 Lake Erie, therefore the distribution was given as the "Great Lakes." 

 Nash's reference was similarly due to a misconception. 



