38 



MEMOIES OF THE CAENEGIE MUSEUM 



number of dorsals, absence of lumbars, rigidly coossified sacrals, are all characters 

 found to be remarkably constant in birds, more especially in Struthio and other 

 Ratites. They are, however, doubtless adaptive rather than genetic and are certainly 

 indicative of no very close relationship. The one represents a condition found in 

 highly specialized sauropod Dinosaurs, the other in comparatively generalized 

 struthious birds. The two groups may have been derived from a common ances- 

 tral stem, or the former have given origin to the latter, but the very similar verte- 

 bral characters just noticed have without doubt been independently developed in 

 either instance. The long tail of Diplodocus is essentially reptilian and contrasts 

 strongly with that region of the vertebral series in recent birds, and is hardly ap- 

 proximated even by Archeeoptei-yx among fossil birds. 



The principal dimensions of the several vertebrae in Diplodocits skeleton No. 84 

 are given in the following table : In column 1 the greatest expanse of the transverse 





1 



2 



3 



4 





mm. 



in. 



mm. 



in. 



mm. 



in. 



mm. 



in. 



1 cei-vical. 



















2 " 







165 



^ 



54 



2tV 



171 



6f 



3 







243 



9i 



69 



2f 



200 



n 



4 







289 



111 



81 



H 



210 



81- 



5 " 







372 



15 



94 



^ 



234 



9| 



6 







442 



17| 



99 



4 



281 



11 



7 







485 



19 



114 



4J 



323 



12| 



8 







512 



20i 



120 



4f 



344 



13^ 



9 







525 



20| 



159 



61 



375 



14f 



10 







595 



23f 



175 



6| 



383 



15 



11 







605 



23|- 



210 



8i 



392 



151 



12 " 







627 



24| 



225 



8i 



433 



17 



13 " 







638 



251 



231 



n 



495 



18| 



14 " 







642 



251- 



295 



111 



529 



20f 



15 " 







595 



23f 



245 



9| 



542 



211 



1 dorsal. 







510 



20rV 



255 



10 



614 



m 



2 " 



534 



21 



416 



16f 



233 



n 



691 



' 271 



3 " 



724 



28 J- 



326 



121 



311 



m 



722 



28f 



4 " 



722 



28f 



318 



12J 



343 



13^ 



718 



281- 



5 " 



650 



25f 



255 



10 



300 



Hi- 



781 



30f 



6 " 



653 



25| 



255 



10 



280 



ll 



793 



m 



7 " 



618 



24^- 



264 



lOf 



280 



11 



810 



3H 



8 " 



595 



23| 



275 



m 



309 



m 



847 



32| 



9 " 



552 



21f 



290 



11^ 



288 



iiA 



946 



371- 



10 " 



585 



23 



267 



lOJr 



313 



12J 



966 



38 



11 " 



530 



20| 



270 



10| 



321 



12| 



1051 



411 



1 caudal. 



710 



271 



183 



7i 



334 



13i 



1049 



411 



2 " 



634 



24J 











995 



39J 



3 " 



660 



26 







332 



13rV 



897 



351 



4 " 



590 



23^ 



250 



9| 



330 



13 



830 



32-1 



5 " 



533 



20 H 



250 



9f 



325 



12| 



777 



30i«5 



6 " 



527 



20| 



237 



9| 



309 



12J 



744 



291- 



7 " 



553 



21| 



237 



9| 



317 



12i 



690 



27i 



8 " 



519 



20f 



246 



9fJ 



309 



12i 



675 



26J 



9 " 



502 



19f 



270 



10§ 



300 



lift 



651 



25| 



10 " 



442 



171 



269 



lOJ 



295 



111 



610 



24 



11 " 



377 



14| 



269 



10| 



285 



lli- 



610 



24 



12 " 



295 



llA 



295 



11t\ 



272 



lOH 



576 



22-1 



