556 THE AMERICAN NATURALIST. | [Vor. XXXIV. 
Amblystoma, and many of the proportions are closely similar, 
and this similarity extends to the internal organs, which are 
even more like those of the ordinary form of Amblystoma 
than are the external parts. In point of size it greatly exceeds 
the average of Amblystoma and goes beyond the maximum 
reported length by 30 mm. The lengths of fifteen specimens, . 
taken from a collection made at St. Paul, of A. tigrinum 
are as follows: 122, 128, 134, 140, 151, 160, 165, 165, 167, 
170, 185, 187, 200, 204, 220 millimeters. The Dakota speci- 
men is almost 100 mm. longer than the longest of these and 
much more considerably exceeds their average. Cope (89) 
reports a specimen of 250 mm. from Wisconsin, and quotes 
De Kay for another of 280 mm. The Dakota specimen thus 
exceeds the recorded maximum length of Amblystoma by over 
one inch. A special detailed comparison of the dimensions of the 
separate organs will be made in connection with each of them, 
and we may pass at once to a survey of them in succession. 
There is a considerable difference between the Dakota speci- 
men and the adult amblystomas in the character of the skin, 
both as to coloration and as to the character of the surface. 
As to the former point in this axolotl the general color is dark 
livid blue, with a lighter area in the middle dorsal region, 
instead of the jet-black color found dorsally everywhere in A. 
tigrinum. On this ground are occasional large circular dark 
spots. This coloration is in marked contrast with adult 4. 
tigrinum, where we find bright yellow spots of a great variety 
of irregular shapes, often elongate and confluent, and with 
either S. mexicanum or S. lichenoides. In the former “a 
pinkish gray ground is covered with numerous small, round, 
dusky spots rather closely placed ” (Cope, '65, 89), and in the lat- 
ter the ground color is blackish brown, with irregular patches 
of grayish yellow, * reminding one of the growth of lichens " 
(Baird and Girard, '52, p. 336), much as in the adult form of 
A. tigrinum; while in Baird's S. gracilis the body is marked 
with very small and numerous dark spots that give it a decid- 
edly mottled appearance. 
In addition to this difference in coloration the skin of the 
Dakota form differs from the texture of the adult and, as far 
