NECTURUS MACULATUS. 589 
the former to an increased number of the elements involved. The ground color of the 
skin, as may be seen on the ventral side, which is mainly free from pigment, is yellowish 
or pinkish, but over the sides and back varying degrees of pigmentation produce different 
shades of slate color, in places with a distinct bluish or purplish tint. The deepest pig- 
mentation is that of the dorsal side where certain densely pigmented areas form irregu- 
larly rounded black spots upon a bluish-slate background, thus suggesting the specific 
name of “ maculatus.” * 
The skeleton consists of several independently separable portions and, like that of 
other Urodeles, contains a large amount of unossified hyaline cartilage. By far the 
largest portion consists of the vertebral column, the skull, to which is attached the hyo- 
branchial complex, and the posterior extremities, which are attached by the ilia to a single 
sacral vertebra. The two halves of the shoulder girdle are free from one another and 
from the rest of the skeleton, and they, with their corresponding free limbs, form two dis- 
tinct skeletal parts. The remaining skeletal elements are the nasal and optic capsules, 
the two laryngo-tracheal cartilages, and the series of rudimentary sternebra which lie in 
the mid-ventral thoracic region. All of these latter parts are wholly cartilaginous and 
entirely disconnected from other parts of the skeleton. 
In arranging the descriptive material of this memoir, the above practical division of 
the skeleton has been taken into consideration as well as the more usual morphological 
one, and it has seemed best to arrange the subject in the order following. In this the 
vertebral column will be first treated, together with the ribs and sternum. The visceral 
arches and the free sense capsules will be treated with the skull, and the limbs and their 
girdles will appear last. This brings the parts together in their topographical relation- 
ships and will be found more practical than a wholly morphological division. 
THE VERTEBRAL CoLUMN. 
General Description. 
The vertebral column, as is the case with fishes, shows little regional differentiation, 
since the limbs are too small and weak either to modify the motions of the trunk by the 
muscles attached to them, or to bring their places of attachment into prominence as 
points of leverage or support. The only gain in this respect over the condition seen in 
1 Just as this manuscript leaves my hands, I have received from Mr, Alexander Nielsen, of Venice, Erie county, Ohio, 
an extensive dealer in Necturus, a specimen having a totally different coloring from the usual one, and Mr. Nielsen, who 
has caught thousands of specimens, writes that it is the first of the kind he has ever seen. The ground color of this speci- 
men is alight reddish buff, with no suggestion of the usual dark slate color. The back is covered with dark brown spots, 
smaller than in the normal forms. In form and size it closely resembles the common species, 
