VERTEBE^ OF VEETEBRATA. 



433 



wliicli is ordinarily known as tlie urostyle (Fig. 225, c), is formed 

 from the rudiments of a few vertebrte ; counting this then, no more 

 than ten vertebral segments can be made out. There are many 

 more in the Urodela ; Amphiuma has as many as 

 100; Menopoma, 48; Salamandra, 42; and the 

 CoecilifB, about 230. 



The transverse processes (tr) are small in the 

 Salamandrina ; the anterior ones are genei'ally 

 divided into two segments ; in the Anura they 

 are larger, but not divided. The superior spinous 

 processes are always rudimentary. Articulations 

 between the arches of the vertebrte are very 

 common, and are effected by the formation of 

 paii'ed articular processes. 



The connection between the pelvic girdle and 

 the vertebral column does not only more dis- 

 tinctly mark off the caudal portion from the 

 region of the trunk, but a sacral portion is thus 

 represented by a vertebra, which is generally 

 distinguished (and especially in Pipa) by the size 

 of its transverse processes. 



GESENBAru, Unters. iiber die Wirbelsaule der Amplubieii. 

 Leipzig, 1861. 



§ 332. 



Fig. 225. Verte- 

 bral colli mn and pel- 

 vis of the Frog. 

 tr Transverse pro- 

 cesses, s Sacral ver- 

 tebra, c Urostyle. 

 il Ilium, is Iscliium. 

 / Femur. 



The rudiments of the vertebral column are 

 developed around the chorda dorsalis of the Sau- 

 ropsida, as of the Amphibia. Arches, which enclose the spinal 

 canal, are given off by the cartilaginous centra. The notochord 

 is also constricted between the vertebrae (cf. Fig. 222, D), but 

 the whole of it eventually disappears (except in the Ascalobota). 

 The continuous rudiment is separated into centra in just the same 

 way as in the anourous Amphibia; in the Saurii and Ophidii, the 

 centra are procoelous. In the Crocodilini and Aves the cartilaginous 

 portions of the rudiment, which lie between the centra in the cervical 

 region, are converted into a special intervertebral apparatus. 



Articular processes extend from the superior arches to the 

 vertebra next in front and behind. They are greatly developed 

 in the cervical region of the Chelonii. The superior spinous 

 processes vary in size, especially in the dorsal region ; in the 

 Crocodilini and many Saurii they are present on the caudal ver- 

 tebrae. Transverse processes are either given off from the centrum 

 itself, or quite close to it. They are greatly developed in the dorsal 

 and caudal region of the Crocodile, but much more so in the Chelonii, 

 where they are surrounded by the bony plates of the dorsal shield, 

 which have been developed in the integument. They are seen to be 

 divided into an upper and a lower portion in the Ophidii. In the 



2 F 



