NECTURUS MACULATUS. 401 
the rhomboidal sternal plate of the higher Urodela, and it would seem probable that this 
latter has resulted from the development of this piece alone. The sternebrum associated 
with the 3d myocomma forms a long and slender open V, which may or may not be 
continuous with the sternebrum of the 4th. Sternal elements are often found both in the 
2d and in the 5th myocomma, usually as a pair of cartilages, or as a unilateral piece. 
Of these, the one associated with the 5th myocomma is much the more frequent, being 
found in rather more than half of the specimens thus far examined, either upon one side 
or both. Sternal elements in the 2d myocomma are rarely seen. 
Ribs. 
These have already been partly described with the transverse processes of the ver- 
tebrae. In the larva they are cartilaginous and are directly continuous with the two 
cartilaginous rods enclosed in the osseous transverse process, and are thus bifurcated at 
their proximal end. During the later process of ossification the 
ribs become ossified as separate pieces and the cartilage remain- 
ing between the proximal ends of the ribs and the sheaths of the 
vertebral rods becomes divided across, thus furnishing two sets of “és 
articular cartilages. By the shape of the first two ribs in the ies 
adult, it would seem that both of the rods are equally involved and bs 
simply fuse to form the ribs, but farther down the ventral or capit- NS 
ular attachment retains its full size and importance, while the am 
dorsal one, although more in the same line with the free end, FS 
becomes much reduced, and in many-vertebrae its attachment is 
merely ligamentous. Thus, described anatomically, the ribs of the ae 
2d and the 3d vertebrae possess almost equal capitular and tuber- 
cular heads, and show a tendency to become bifurcated at their age 
tips. In the ribs of vertebra 4 to 6 the two heads are still almost 
equal but the distal part of the rib is a simple rod; and farther = 
“SS 
: . yh 
down, from about the 8th vertebra on, the capitular head forms 
the main attachment, and meets at a decided angle the straight Fig. 7. Ribs taken from 
piece formed by the free end and the tubercular head. The sacral EI Tee A Ly 
and placed so as to show 
rib possesses two very large and equal heads, but is not bifurcated 
the anterior aspect. The 
distally, and beyond the sacrum the rib element is a variable tubercular head is above 
quantity (v. sup.). It would thus seem, judging from purely puck tle. captiulan below, 
The numbers refer to the 
anatomical evidence, that the condition described by Géppert  sttebea to which cashiean 
as characteristic of Necturus is not a universal one applicable to belongs. X 2. 
