312 



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



The differences are shown in the following tab>ilar arrangement :- 



Serial 

 number of 

 TerfcebrEe. 



JRh. amcricana. 



Last cervical or 

 transitional rib . 



Free rib 



1st sternal rib' ... 



2nd 



3rd 



4th 



1st lumbar 



2ud „ 



3rd lumbar, anky- 

 losed with ilium . 



Acetabular process 



Rh. darwrni. 

 ?. I 3. 



Eh. macrorhynaha. 



[trans, rib. 

 Last cervical or 



Last cervical or trausi 

 tional rib. 



Free rib 



Free rib j Free rib. 



1 st sternal rib I Free rib. 



2nd sternal rib i 1st sternal. 



3rd sternal rib I 2nd sternal. 



1st lumbar i 3rd sternal. 



2nd lumbar \ Ist lumbar. 



3rd lumbar, anky- 2nd lumbar 

 losed. 



3rd lumbar. 



Acetabular processes . . . 



No transverse processes connecting the ilium 

 witli the vertebral column. 



The two primitive sacral vertebrae. 

 Last connection with ilium. 



I Acetabular. 



No transverse 

 processes. 



Last connection with ilium. 



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 Rhea. 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 tliis rib the intermediate or transitional one, because it 

 forms 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 sjiecimens of Rh. darwini, in Dr. Cunningham's Rh. darwini 

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

 two do not reach the sternum, wanting the sternal connecting 



'^ Cunningham saya that in the two specimens of Ek. americana and Bh. 

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

 nected with the sternum. Tlie Same is the case with the specimen of Bk. 

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

 Heidelberg and the Cambridge specimens of Bh. americana possess four pairs 

 of sternal ribs, each of whichis furnished with an uncinate process. TJie number 

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

 of the neck-vertebr» were wanting in Cunningham's specimen of Bh. dartvitii. 



