68 The Pickerel-frog, Rana palustris LeConte. 



nearer the base of the hind legs than the end of the snout, average 1.6. 

 Anus dextral. Depth of the tail in its own length 2.3 to 3.2, average 

 2.7. Depth of the muscular part of the tail 1.8 to 2.2 in the depth of 

 the tail. Mouth is contained 0.85 to 2.1 times in interorbital distance, 

 average ] .45. Greatest length, 74 mm. Greatest length of body, 26 mm . 

 Greatest length of tail, 49 mm. Greatest depth of tail, 16 mm. 



Coloration of body (Plate ix, Fig. If) : Background of back olive- 

 green shading through yellowish on the sides and front of head to cream 

 on the venter, the back being marked with fine black and yellow spots. 

 The yellow is more marked at the base of the tail and in the region of the 

 mouth. Blotches of white pigment occur on the belly. From the gill 

 region forward, black as well as white pigment is prominent. The whole 

 venter is conspicuously iridescent. The tail is very dark, particularly 

 toward the tip; the whole marked with fine black and golden-yellow 

 punctulations, the yellow ones usually aggregate ; these groups of yellow 

 spots are more numerous toward the base of the tail. In some speci- 

 mens the dark punctulations are so numerous as to make the tail 

 'purplish black, a condition (when present) making these tadpoles almost 

 as distinctive as the vermilion-tailed tadpoles of Hyla versicolor. 



Mouth-parts (Plate viii, Fig. 2) : Labium and papillae without black 

 punctulations, as in the green-frog and the bullfrog. Upper rows of teeth 

 in two series; the first is the upper continuous fringe bounding the lip's 

 margin; the second is a row on either side, the median space between 

 them being at least twice the length of either lateral row of this series. 

 The lower 3 rows are after the green-frog plan. The first lower row 

 is frequently broken in the middle. The upper fringe is seldom dis- 

 continuous unless injured; the second upper row of either side is almost 

 invariably present, sometimes absent on one side, very rarely on both 

 sides or faint on both sides. In 67 tadpoles examined, only four had 

 this row missing. The lower second is occasionally discontinuous in 

 the middle, but not so frequently as in R. catesbeiana. More rarely the 

 third row may be discontinuous. In three specimens the lower teeth 

 rows were in decided disorder. 



THE LARVAL PERIOD. 



The developmental period consumes about 90 to 100 days. In 1906 

 the first eggs recorded were April 25 and the first transformed example 

 appeared July 24, an interval of 90 days. In 1907, in two different 

 places (one a pond, the other a backwater) the first eggs were laid 

 April 30, and 95 days later (August 3) the first transformed pickerel- 

 frogs were observed in the same places. These eggs hatched in 14 

 or 15 days, thus giving a true larval period of about 80 days. In 1909 

 we have one record of 91 days. In 1911 the period from egg to trans- 

 formation was 87 days, or 76 days of true larval life, for the eggs 

 hatched in 11 days. 



