E 
No. 419.] THE ANATOMY OF AXOLOTLS. 889 
The external characteristics are indicated in Fig. 1, which 
is drawn from specimen No.2 of the following lists. In the 
account which now follows, the siredon described as the type 
of the collection is No. 2. It will be compared with the other 
siredons, with No. 10, a metamorphosing specimen, and with 
adult specimens of Amélystoma tigrinum from the collection in 
the museum of Hamline University, from St. Paul, Minn. 
The coloration (of the formalin material) is uniform and 
not mottled or spotted. The head and trunk are dark above 
and light beneath, the division line running from the jaw along 
the side of the head and on the body on the level of the 
ventral borders of the limbs. The post-abdomen, or “ tail,” is 
dark throughout, as are also the dorsal and ventral folds of 
skin, “fins.” One of the larger specimens (No. 8) differs 
from the rest in being distinctly spotted. The spots are very 
numerous and small, about 1 mm. across, and are found in all 
parts of the dark area of the animal. Both of the Dakota 
specimens are spotted, as can be seen by a reference to Fig. 7 
of this article and Fig. 1 of the preceding. In both of these, 
however, the spots are fewer and larger and more distinct. 
Baird's S. gracilis (59 Vol. X, Pl. XLIV) is also spotted, and 
the Colorado specimen is more like to it, according to the illus- 
tration, than to the Dakota forms. In the smaller specimens 
of the Colorado collection the dorsal darker area is not uniform 
in tone, but is mottled with dark irregular patches scattered 
irregularly upon it. These patches are not distinctly bounded, 
but shade into the general color tone at the edges, and are 
very irregular in shape. They also extend out upon the dorsal 
and ventral fins. 
The head in the Colorado specimens differs markedly from 
that of terrestrial amblystomas in several particulars. - In 
order to afford the opportunity to test some of these points, 
I give a number of measurements made on specimens of 
Amblystoma found at Hamline, Minnesota. I may say that 
these are fully metamorphosed and strictly terrestrial. | 
By dividing the length of the head, from the snout to the 
fold Crossing between the bases of the hinder gills, by the 
length from the chin to the posterior boundary of the cloacal 
