3^ 



THE AMERICAX XATrR. 



column, and, according to their Icngtli. form a nioie or k-ss com- 

 plete osseous covering and protection to the vertebral artery 

 during its passage between anv two contiguous foramina." 



Then after describing the neural and hicmal spines of the 

 cervical vertebrae"; the axis and the atlas, Coues proceeds by 

 saying that, " If we consider the dorsal as corresponding in 

 number with the ribs, we should assign ten to this portion of 

 the column. The last three ribs, however, correspond to verte- 

 brae which are completely anchylosed to the sacrum as well as 

 to the iliac bones, and at the same time they differ in several 



respects from the dorsal ribs proper " 



The transverse processes of these [dorsal] vertebra? are as 

 usual very broad, long, and thin ; their posterior border concave, 

 their anterior convex, and their postero-external angles pro- 

 longed backwards into a short ' styliform ' process, more or less 

 intimately connected with the next succeeding vertebra. The 

 horizontal lamellae of the transverse processes of the last four 

 vertebrae are pierced by a quite large foramen." 



*' The superior spinous processes of the vertebra; are so long 

 that they nearly touch each other by their anterior and posterior 

 borders ; only a slight space being left between them. They 

 are quite regularly rectangular in shape, having straight, flat 

 superior borders at right angles with the anterior and posterior 

 borders. They are connected with each other by dense and 

 strong ligaments, and probably become more or less completely 

 anchylosed with age." He then carefully describes the enor- 

 mous development of the haemal spines of the dorsal vertebr£e, — 

 and although of much the same shape, the one for U. liinime 

 {Jour. Anat. and Physiol) gives but a feeble idea of their remark- 

 able development in Urinator imber, the subject of the memoir 

 from which I have been quoting. Among themselves the 

 motion of the vertebras during life in this dorsal region of the 

 column is wonderfully restricted, and as I have shown above, in 

 some grebes the dorsal vertebrae all fuse into one common piece. 



Coues made out 15 vertebrae as being fused together in the 

 pelvic sacrum ; but in a specimen before me, after careful count, 

 there appear to be sixteen. Marsh found but 14 in the sacrum 

 of Hespcrornis regalis. 



