432 HARRIS HAWTHORNE WILDER ON 
from the rib previous to the sacral rib to the dorsal end of the ilium; and in one of these 
which I have had the opportunity of examining more closely, the sacral rib on the right 
is normal and attached to what is probably the 19th vertebra, while the sacral rib upon 
the left side proceeds from the next posterior vertebra (20th). In addition to this, a 
strong but narrow ligament proceeds from the free end of the previous rib (19th) and 
inserts upon the dorsal end of the ilium anterior to the attachment of the sacral rib. 
As this fragment came from a student’s preparation, the remainder of which had been 
lost, the exact determination of the vertebrae cannot be made, but judging from the 
other cases of oblique attachment which have been reported, the numbering is undoubt- 
edly as given. ‘This case resolves itself into one of “ oblique attachment,” such as have 
been reported by G. H. Parker, Waite, and Bumpus, the obliquity being dextro-sinistral 
(see above, under Vertebral Column). 
The Free Limbs. 
The serial homology between the fore and hind limbs in Necturus is very striking, 
and in so primitive an animal, perhaps the most primitive one possessing a cheiropte- 
rygium, points to a fundamental similarity of origin. It is thus of greater morphological 
interest than correspondences in such modified structures as the paddles of Ichthyosaurus 
where it is likely that the similarity is a secondary modification due to a similar method 
of use. This resemblance, which is apparent externally, is still more emphasized by the 
skeletal parts, and it seems incongruous to find such similar free limbs attached to such 
different girdles. Each limb terminates in four digits, the lost member being generally 
considered to be the first, and the phalangeal formula, 2—2-5-2, is the same in both 
manus and pes." 
With the exception of carpus and tarsus, which are wholly cartilagimous, the limb 
bones of the adult consist each of a bony shaft running through the middle, and two 
cartilaginous epiphyses, a slight exception being the terminal phalanges which are without 
epiphyses at the distal end. The shaft, or diaphysis, ossifies perichondrially, as always in 
the Amphibia, and forms a tubular sheath of bone, thick and constricted in the middle of 
its length and tapering at the ends to thin edges, the whole mass being something like 
the centrum of a biconcave vertebra considerably prolonged in the direction of its length. 
The epiphyses always remain purely cartilaginous, and never obtain calcareous deposits as 
in the frog. 
‘On this point Cope (°89, p. 25-28) seems to have made a singular mistake, giving the phalangeal formula for N. 
maculatus as 1-3-8-2 for the manus, and 1-2-2-2 for the pes. For the rare Carolina form, N. punctatus, he gives the 
formula 2-2-3-2 for both limbs, which corresponds to the normal condition in N. maculatus and is undoubtedly character- 
istic of the entire genus. 
