406 THE OSTEOLOGY OF VULPES MACROTIS. 



this part of the column. Laterally the heads of the ribs u}3on either side articulate 

 between the facets of the centra, except in the last two pair, where they articulate 

 entirely upon the body of the vertebra to which they belong. From the eighth 

 thoracic to the ultimate lumbar inclusive the vertebrae increase in size and con- 

 spicuousness. The neural spines, situated upon the fore part of the centra, lean 

 forward, and are thin, narrow and laterally compressed. We find the tallest in 

 the middle of this series, while the zygapophyses are strongly tilted upward in 

 the last three dorsals and leading lumbar, to become slightly less and less so as the 

 pelvis is approached. 



The transverse processes, bent downward, forward and outward, are narrow, 

 thin, sharp plates, compressed from above downward, and in the last of the series 

 have somewhat dilated ends. They are hardly to be noticed in the last three 

 thoracics, but after that they gradually commence to lengthen, until those on the 

 last two lumbar vertebrae attain a length of two centimeters each. The neural 

 canal appears to have the least calibre in the post-thoracic region, and the greatest 

 in the pre-cervical and post-lumbar. Throughout the chain at their ordinary sites 

 in the carnivora, the usual foramina exist between the vertebral centra for the exit 

 of the pairs of the spinal nerves. 



The three sacral vertebrce are all firmly anchylosed together, and present, both 

 dorsally and ventrally, two pairs of neural foramina. Small neural spines are also 

 present, but no haemal ones. With respect to size, the first sacral is the biggest. 

 It and the second offer strong lateral abutments for the ilia of the pelvis. It is 

 only the fore part of the last sacral that does this, — the postero-lateral processes of 

 this vertebra being free and directed backward and outward. Somewhat similar 

 ones are developed upon the four leading caudal vertebrae, but the rest of the series 

 of those in the tail become more and more rudimentary and elongated as we pass 

 toward its tip, the last few again shortening, to become mere rodlets of bone, with 

 barely any semblance whatever to a true vertebra. 



The Sternum. — Agreeing with other small vulpine forms among the Canidae, 

 this part of the skeleton in Vulpes macrotis consists, of eight pieces, — one being the 

 presternum, one xiphisternum, and six pieces in the mesosternum. These latter 

 decrease in size from before backward, being in any case but small subcylindrical 

 rods of bone with enlarged extremities. They meet each other in subcircular disc- 

 like articulatory facettes, the mesial extremities of the cartilagimous costal ribs 

 articulating between them, one upon either side. The xiphisternum is represented 

 merely by a long very slender piece of cartilage, while the presternum is longer 

 than any of these sternal segments. 



Rather more anteriorly than midway on its shaft dorsad, there is a small pair 

 of facettes, one upon either side, with which articulate the first pair of costal ribs. 

 The apex of this piece of the sternum is bluntly rounded off. The second pair of 

 costal ribs articulate at the junction of the presternum and first piece of the meso- 

 sternum, while at the junction of the last piece and the xiphisternum two pairs of 

 costal ribs articulate, and the extremities of a "floating pair" approach this point. 



