374 



ZOOLOGY 



SECT. 



central perforation through which a suspensory ligament passes 

 from one centrum to the other. 



The first two vertebrae, the atlas and axis, resemble those of the 



s.scr 



CL.tr 



cd v 



ftu, 



a 



3V9 



n.ot 



car- 



FIG. 1038. Columba livia. The bones of the trunk, acr.cor. acrocoracoid ; a.tr. anti- 

 trochanter ; actb. acetabulum ; car. carina sterni ; cd. r. caudal vertebra; ; cor. coracoid ; 

 cv.r. cervical ribs ; f.trs. probe passed into foramen triosseum ; fur. furcula ; gl.cv. glenoid 

 cavity ; il. ilium ; is. ischium ; is. for. ischiadic foramen ; obt.n. obturator notch ; pu. pubis ; 

 pyg.st. pygostyle ; scp. scapula : s.scr. syn-sacrum ; ft. sternum ; st. r. sternal ribs ; th.v. 1, 

 first, and th.v. 5, last thoracic vertebra ; unc. uncinates ; vr.r. vertebral ribs. 



Lizard, but have the various elements of which they are composed 



completely fused. The small size of the ring-like atlas is noticeable. 



Between the last cervical vertebra and the pelvic region come 



either four or five thoracic vertebra? (Fig. 

 1038) the first three, when four only are 

 present, the second, third, and fourth, when 

 there are five, united into a single mass, the 

 last free. The anterior thoracic as well as 

 the posterior cervical vertebra have the 

 centrum produced below into a compressed 

 plate, the hypapophysis, for the origin of 

 the flexor muscles of the neck. They all 

 bear ribs, each consisting of a vertebral 

 (vr.r.) and a sternal (st.r.) portion, and 

 articulating with the vertebra by a double 

 head. The sternal, like the vertebral rib, is 

 formed of true bone, not of calcified carti- 

 lage as in Reptiles, and articulates with 



zyg. anterior zygapophysis ; J. .... 



en. centrum; n.a. neural the vertebral rib by a synovia! joint. 



crv 



crv 



FIG. 1039. Columba livia. 



Cervical vertebra. A, an- 

 terior, B, posterior face. o. 



verte'brarteriai foramen. 



Springing from the posterior edge of the 

 vertebral rib is an uncinate (unc.), resembling 



that of Sphenodon and the Crocodile, but formed of bone and 



ankylosed with the rib. 



