AVES. 



93 



"Wall-ease 

 25. 



species, Aepyornis titan and A. maxiiiULS, but it is worthy of Wall-case 

 note that in the New Zealand Apteryx the egg is enormous ''^^q 



compared with the size of the bird which lays it (see Case GG). 

 The living rheas of South America were preceded in the 

 Tertiary period by large birds like Brontornis, of which 

 plaster casts of limb-bones are exhibited in Wall-case 25. 

 The two-toed ostriches, which are now confined to Africa 

 and Arabia, ranged into the Indian and south-eastern 

 European regions in Pliocene times. Eemains of Struthio 

 asiaticus from the Siwalik Formation of India are placed 

 with the skeleton of a modern ostrich in Case EE. A Case EE, 

 small piece of limb-bone from the Eocene of the Fayum, 

 Egypt, exhibited in Table-case 12, prolmbly represents an 

 ancestor of the ostriches, which has Iieen named Ercmopezus 



eocaenus. 



Order III.— SAURURJE. 



Birds are proved by their structure to be closely related Table-case 

 to reptiles ; and many of the extinct reptiles exhibit pecu- ^^' 



liarities which are now exclusively confined to birds. It is 

 therefore interesting to observe that the oldest known birds, 

 which date back to the latter part of the Jurassic period, 

 approach the reptiles more nearly than any existing birds in 

 at least four respects. They are peculiar in (1) the possession 

 of true teeth, (2) the Ijiconcave or flat-ended shape of their 

 vertebraB, (3) the completeness of three clawed fingers in the 

 wing, and (4) the elongated, not tufted, shape of the tail. 

 In allusion to the last-mentioned feature they are named 

 Saururffi (" lizard-tails "). 



Of these primitive bu'ds only two satisfactory specimens 

 have hitherto been discovered, both in the Lithographic 

 Stone of Bavaria, which is of the same geological age as the 

 Kimmeridge Clay of England. They seem to belong to two 

 species of one genus, and the first specimen, representing 

 ArcliiBoptcryx macrura of Owen, is shown in Table-case 13. 

 The piece of limestone in which the skeleton is preserved has 

 split along the plane of weakness caused l)y the presence of 

 the fossil itself, so that some of the l)ones adhere to one face 

 while other portions are retained by the counterpart slab. It 

 is thus necessary to exhibit the two slabs side by side, the 

 one supplementing the other. As shown by the accompany- 

 ing photograph (Plate VI) and the explanatory diagram 

 (Fig. 87), there is a typical bird's " merrythought " (furcula) 



