1870. | AXIAL SKELETON OF THE URODELA. 271 
The transverse processes at their roots, 7. e. near their origin from 
the centrum, are often traversed by a canal passing from behind 
forwards and transmitting an artery. This is well seen in Crypto- 
branchus, Menopoma, Menobranchus, and Salamandra. 
Riss. 
With the exception of the genera Amphiuma, Siren, and Proteus, 
all the transverse processes of the dorsal* and sacral regions support 
ribs, and not unfrequently the anterior caudal ones also. 
The first vertebra of all, however, even when furnished with a 
rudimentary transverse process, remains always destitute of such bony 
appendages. 
The ribs form a series of evlindroidal bones (figs. 11, 12, 13 & 18), 
each extending outwards and more or less downwards and backwards, 
and ending distally in a free pointed termination, with the exception 
of the single pair attached (one on each side) to the hip-girdle. 
They never have cartilaginous or osseous parts attached to their distai 
ends and answering to the sternal ribs or cartilages of most higher 
vertebrates. Rarely, as in more or fewer of the ribs of Avoloél and 
Amblystoma, they extend rather upwards and backwards. The 
number of ribs varies from five or six pairs in Amphiumat, eight in 
Siren t, seven, eight, or nine in Proteus § (if the second vertebra bears 
any) to some twenty-one or twenty-two pairs (counting the caudal 
ribs) in Menobranchus and Cryptobranchus. Proximally the ribs 
very commonly bifurcate into two short and nearly equal branches, 
diverging from each other at a more or less acute angle (fig. 12). 
These branches are placed one above the other, and are attached 
respectively to the tubercular and capitular parts or processes of the 
respective transverse processes. The upper branch of this fork may 

Lateral view of first four vertebrae of Siren (No. 576B in Museum of College 
of Surgeons). 
thus be called the tubercle (¢uberculum) of the rib, and the lower 
branch its head (eapitulum). When, as in Siren, Menopoma, and 
Cryptobranchus, the distal articular surtaces of the transverse pro- 
cesses are near together, the proximal ends of the ribs do not bifurcate, 
* Rusconi represents none to the first dorsal of Proteus. 
+t Cuv. Mém, du Mus. vol. xiv. 1827, p.9. ‘The College of Surgeons speci- 
men looks as if it had had ten pairs at least. 
{ Cuv. Oss. Foss. 4th edition, vol. x. p. 350. 
§ Cuvier (/oc. cit. p. 358) says seven, counting from the second vertebra. Rus- 
coni represents seven, beginning with the third vertebra: the last is so small as 
to be with difficulty detected. - 
