Ranidae 



Rana virgatipesis decidedly a water frog, and is one of the least 

 hardy of the North American species. It has only average powers 

 of leaping and swimming, but its instincts for hiding are strong. 

 When disturbed, it disappears at once under floating water-weeds. 



It differs from the other smaller frogs of North America in the 

 great development of the eyes and ears. It is like the bullfrogs 

 in lacking the lateral folds. It resembles the Leopard Frog, 

 in that the male frog has large vocal sacs that can be extended 

 at the sides behind and under the ears. It shows close relation- 

 ship in structure and habit to Rana grylio (pp. 227 to 227). 



THE NORTHERN FROG 

 Rana sepientrionalis Baird 



IDENTIFICATION CHARACTERISTICS 



Colour: Light olive, with or without coarse vermiculations 

 of darker colour. There may be large irregular blotches of 

 brown on the sides and posterior back. No light stripe along the 

 jaw. Legs blotched or transversely banded. Underparts light yel- 

 lowish, unspotted. Buttocks yellow, with dark blotches. Posterior 

 surface of femur may be strongly reticulated with dark colour. 



Measurements: Size medium, i. e. length 2 to 3 inches. Leg 

 measurement to heel equals body measurement forward to the 

 eye. Tibia and femur about equal in length. 



Structure: Skin relatively smooth; finely pitted when ex- 

 amined closely. Underparts smooth. Buttocks but slightly 

 granulated. Body rather stout. Head narrow, rounded in 

 front. Space between the eyes narrow. Nostrils large, half- 

 way between eyes and tip of muzzle. Ear larger than the eye 

 in the male, smaller than the eye in the female. No lateral 

 folds, or only slight traces of them. Feet long, toes provided 

 with long, broad webs. Inner sole tubercle medium in size. 



Range: Rana septentrionalis is wholly northern in its dis- 

 tribution. It is reported from the Adirondack Mountains, 

 from Lucknow, Ontario, and Fort Ripley, Minnesota, and from 

 Moose River and the Hudson Bay region. 



It is thought that this species is intermediate in its charac- 

 teristics between some more primitive form and nearly all the 



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