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DK. H. GADOW ON THE SPECIES OF RHEA. [Mar. 17, 



The postsacral region, beginning with the 37th or 38th vertebra 

 respective!)', shows in all the specimens the almost complete 

 resorption of the vertebral column which is typical and so remarkable 

 of the genus lihea. In Rh. americana and in Rh. darwini the 

 first 14 cervical vertebrae possess, with the usual exception of the 

 atlas and epistropheus, the typical avian cervical ribs, which anky- 

 lose firmly with the dorsal and ventral lateral processes of their 

 vertebrae ; their distal sharply-pointed ends are directed parallel to 

 the long axis of the vertebral column. The 15th vertebra carries a 

 short (about 2-3 centim. long), thick and blunt, not moveable, rib. 

 We will call this rib the intermediate or transitional one, because it 

 I'orms the transition from the cervical to the thoracic ribs, or it may 

 also be called pseudo-cervical. Then follow 8 long ribs, of which in 

 our two specimens of Rh. darwini, in Dr. Cunningham's Rh. darivini 

 and Rh. americana, and m Prof. Mivart's Rh. americana, the first 

 two do not reach the sternum, wanting the sternal connecting 



' Cunningham says tiiat in the two specimens of Rh. americana and Rh. 

 darwini examined by hiiu but three ribs (the third, fourth, and fifth) were con- 

 nected with the sternum. Tlie same is the case witli the specimen of Rh, 

 americana in the Royal College of Surgeons examined by Prof. Mivart. The 

 Heidelberg and the Cambridge specimens of Rh. uinrricana possess four pairs 

 of sternal ribs, each of whieliis furnished with an uncinate process. Tiie number 

 of sternal ribs is therefore subject to individual variation. About four or five 

 of the neck-vertebrse were wanting in Cunningliam's specimen of Rh, darwini. 



