OCR Text |
Show 312 DR. H. GADOW ON THE SPECIES OF RHEA. [Mar. 17, The differences are shown in the following tabular arrangement:- Serial number of vertebr 15 16 «. 17 18 19 20 21 22 23 24 25. 26 27 28 29 30 31 32 33 34 35. 36 1 1 I 1 1 } I 37 Rh. americana. Rh. darwini. Last cervical or transitional rib Free rib 1st sternal rib x . 2nd 3rd 4th 1st lumbar 2nd „ 3rd lumbar, anky-losed with ilium Last cervical or transitional rib. Free rib Free rib 1st sternal rib Rh. macrorhyncha. [trans, rib Last cervical or Free rib. Free rib. 2nd sternal rib > 1st sternal. 3rd sternal rib 1st lumbar 2nd lumbar 3rd lumbar, anky-losed. Acetabular process Acetabular processes ... No transverse processes connecting the ilium with the vertebral column. 2nd sternal. 3rd sternal. 1st lumbar. 2nd lumbar. 3rd lumbar. I Acetabular. No transverse processes. The two primitive sacral vertebrae. Last connection with ilium. Last connection with ilium. The postsacral region, beginning with the 37th or 38th vertebra respectively, 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. W e will call this 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 specimens 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 says that in the two specimens of Rh. americana and Rh. darwini examined by him but three ribs (the third, fourth, and fifth) were connected with the sternum. The same is the case with the specimen of Rh. americana m the Eoyal College of Surgeons examined by Prof. Mivart. The Heidelberg and the Cambridge specimens of Rh. americana possess four pairs ot sternal ribs, each of which is furnished with an uncinate process. The number ot sternal ribs is therefore subject to individual variation. About four or five ot the neck-vertebra were wanting in Cunningham's specimen of Rh. darwini. |