SKELETON OF CHELONIA. 615 
Similarly, the median pieces are the result of fusion between median 
dermal bones and the neural spines of the vertebre. The plastron 
usually consists of nine dermal bones, and the three anterior pieces 
perhaps represent clavicles and interclavicle (or episternum). 
The eight cervical vertebrse have at most little rudiments of ribs, are 
remarkably varied as regards their articular faces, and give the neck 
many possibilities of motion, There are no lumbar vertebree. 
The bones of the skull are immovably united; there is only a lower 
temporal arcade, formed by jugal and quadrato-jugal; there are no 
ossified alisphenoids, but downward prolongations of the large parietals 
Fic. 332.—Pectoral girdle of a Chelonian. 
G., Glenoid cavity; SC., scapula; P.C., procoracoid fused 
to the scapula; C., coracoid; Z.C., epicoracoid cartil- 
age; L., ligament. : ‘ 
take their place ; neither presphenoid nor orbitosphenoids are ossified ; 
there are no distinct nasal bones in modern Chelonians, their place 
being taken by the prefrontals ; the premaxille are very small; there 
are no teeth. ; : 
There is no sternum. The pectoral girdle on each side consists of a 
ventral coracoid and a dorsal scapula attached to the carapace. The 
‘ scapula bears an anterior process of large size, usually regarded as a 
‘* precoracoid” or procoracoid. ; 
The pelvic girdle consists of dorsal ilia attached to the carapace, 
posterior ischia, and anterior pubes, with pre-pubic processes and an 
epi-pubic cartilage. There is a pubic and an ischiac symphysis. 
The girdles originally lie in front of, or behind the.ribs, but are over- 
arched by the carapace in the course of its development. 
