680 SCIENCE PROGRESS 



the South American Rheas is also possible. On the other hand, 

 this bird may be merely another instance of the results of retro- 

 gressive change, leading to loss of flight and increase of size in 

 some group of Carinate birds, such as has happened in the case 

 of the Stereornithes and Gastornithes. 



Among the Reptilia no very important new forms have been 

 discovered. In the Middle Eocene remains of large and probably 

 marine snakes are found, one of these (Gigantophis) having 

 probably attained a length of 30 to 40 ft. Another {Ptcrosphenus) 

 is of interest, because a closely allied species is found in 

 North America also associated with Zeuglodonts. From the 

 same horizon there have been collected remains of numerous 

 Pleurodiran tortoises, a group formerly widely spread, but at 

 the present day found only in Madagascar and South America. 

 The most remarkable of the Egyptian Pleurodires is Stereogenys, 

 in which the palate and mandible are modified to form broad 

 crushing surfaces, probably for breaking the shells of the 

 animals which formed its food. In the Upper Eocene beds 

 Pleurodiran tortoises are likewise found, the modern genus 

 Podocnemis being represented by several species ; but at this 

 horizon the most notable chelonian is a gigantic land-tortoise 

 {Tcstudo amnion), shells of which are comparatively numerous. 

 This species approximates most nearly to the Aldabara and 

 Madagascar giant tortoises among living forms. Numerous 

 Crocodiles are found both in the Middle and Upper Eocene, and 

 include both long- and short-snouted forms. One {Tomistoma 

 gavialoidcs) seems, to some extent, to bridge the gap between the 

 true Tomistoma and the Gharial. 



Remains of fishes are found in several horizons, but none 

 are of special interest. From the Middle Eocene are several 

 peculiar Saw-fishes, and also several large Siluroids, which 

 are curiously like species now existing in the Nile. 



From the above account it will be gathered that a con- 

 siderable number of Tertiary vertebrates are already known 

 from Egypt, and include forms of great interest. At the same 

 time, these must constitute a mere fraction of the faunas 

 that have inhabited this region, and therefore, since the con- 

 ditions seem to be very favourable to the preservation of 

 vertebrate remains, it is to be hoped and expected that many 

 new types of vertebrate life will be discovered, especially when 

 the desert between the Fayum and the Wadi Natrun can be 



