THE BATRACHIA OF NORTH AMERICA. 



269 



opposite the middle of tlie third phalange of the fourth toe, counting 

 from the end. In tbe extreme southern form the web does not extend 

 to the extremities of the digits, but leaves tbree phalanges of the fourth 

 toe absolutely free. It is notched to a point a little proximal to the 

 distal end of the fourth (first) phalange. Between tbese extremes of 

 palmatiou (represented by specimens 328 and 2581) all the intermediate 

 conditions may be found. The internal metatarsal tubercle is small 

 and narrow, with subconical extremity; the external is a low but rather 

 wide tuberosity. The first finger is longer than the second. 



The northern forms are sometimes of a uniform olive-brown above, 

 with a pale vertebral line, and with the abdomen indistinctly spotted. 

 Sometimes the uniform brown extends for a short distance on each side 

 of the pale A^ertebral line, exterior to which the surface has large brown 

 spots on a light olive ground. In the southern forms the ground color 

 is light brown or olive, or even clay color, with an irregular brown band 

 on each side of the light vertebral line. On each side are large dark 

 brown spots with a reddish wart for a center. Spots on the posterior 

 legs like those on the back. Below unspotted. 



4 7 



Fig. Gi. —Bufo columbiensis halophilus (from Baird, TJ. S. and Mexican Bound Survey) ; 1, 



The northern and southern varieties may be thus defined in extreme 

 forms : 



Head 4.5 times in leugth; web extending to tips of toes, bnt deeply emargiuate; 



parotoid gland more elongate ; colors dark ; size large B. c, columbiensis. 



Head 4 times in length ; webs more deeply notched, and leaving tbree phalanges of 



fourth toe free ; parotoid shorter ; colors light; size smaller B.c.halophilns. 



There are, however, as many specimens which are intermediate between 

 these extremes as there are specimens of the latter. These represent 

 the Bnfo mieroscaplius Co])e. The specimens of the middle and south- 

 ern Rocky Mountain region are referable to it, as well as many from 



