52 ELEMENTARY ANATOMY. [LESS. 



serve to support the bony shell of those animals. In Prio- 

 dontes the meta'pophyses are enormous, and there are four 

 articular surfaces on each side of each end of a lumbar 

 vertebra. 



In addition to the complexity of articulation described as 

 existing on the last dorsal vertebra of the Great Ant-eater, we 

 find in this animal's lumbar region an additional articular 

 surface en each side of each transverse process. 



A long hypapophysis may be developed, as in the Hare. 

 Instead of being free, as in man, the lumbar vertebras may 

 be anchylosed together and with other parts, as in Birds, the 

 Chelonians, and Glyptodon. 



7.S 



P 



FIG. 66. PELVIS OF A BIRD ANCHYLOSED TO THE LUMBAR VERTEBRA. 



</3, last free dorsal vertebra ; c, coccygeal vertebrae ; il, ilium. ( For the other 

 letters see Lesson V.) 



26. Inasmuch as the first two vertebrae and no more are 

 specially modified, man agrees with all birds and beasts, and 

 differs from all below. The specialization may, however, be 

 even greater than in him, as is the case with Chelonians, 

 where each cervical has its own peculiarities. Thus in the 

 common european Terrapin we find the fourth cervical with 

 its centrum convex pre-axially, and concave post-axially ; the 

 fifth is bi-convex ; the sixth is concave pre-axially, with a 

 double post-axial convexity ; the seventh has a double pre-axial 

 concavity and a double convexity post-axially ; the eighth has 

 a double concavity at each end ; the ninth has a double 

 pre-axial convexity and a single one post-axially, and also 

 curiously arched post-zygapophyses. 



The ATLAS of man, in having no true body, agrees with that 

 of all Vertebrates above the Ichthyopsida. In the highest 

 member of that group, the Frog, the first vertebra has the 

 neural arch attached to a centrum just as the other vertebrae 

 have, and at the same time the power of rotation on the 

 second vertebra is lost. 



In having two articular surfaces for the skull, man's atlas 

 differs from that of Birds and Reptiles, but agrees with that 

 of Batrachians and some Fishes. 



