PRO(;.\.\'()SArR/.\ 



129 



ascril)e our lack of knowledge of an}' fossil proganosaurs in tiie 

 Northern Hemisphere to the mcagerness of the fossil records, but 

 there are many other examples of similar import among other early 

 animals. 



The age of the South American proganosaurs is now believed to 

 be lower or lowermost Permian, like that of the African Mcso- 

 saurus; possibly, however, the age first described to Stereostcrnum 

 (Carboniferous) may be correct. 



The known skeletons are all small, none exceeding a few feet 

 in length. The skull, as shown in the figure by Dr. McGregor, is 

 elongate, and its teeth are extraordinarily so, and very slender. 

 The external nostrils are situated close to the eyes; and no sclerotic 

 bones have been discovered. There are small teeth in the bones 

 of the palate. The neck is elongate, composed of ten or twelve 

 vertebrae. The trunk also is long and slender, and the tail is not 

 only long, but also much flattened or compressed. All these 

 are very characteristic of water life. The limbs, however, show 

 a much less complete adaptation for swimming — not much more 

 so in fact than do those of the living Crocodilia. The upper arm 

 and the thigh bones are relatively long, while those of the forearm 

 and the leg are shorter than among terrestrial reptiles, the first 

 indication of swimming habits to appear in crawling animals. The 

 digits are not much elongated, and they have no additional finger 

 bones, save perhaps in a lately discovered form in Africa, in which 

 Dr. Broom reports supernumerary bones in the fifth or "little" 

 toe.* The fingers and toes have only blunt terminal bones, that is, 

 they were not distinctly clawed, and they were probably connected 

 with each other by a membrane, as in a frog's foot. This webbing 

 of the feet is probable, not only because of the positions in which 

 the bones have been found, but also because of the great length of 

 the "little" toe, which is the longest in the foot, a character quite 

 abnormal for a land reptile and quite characteristic of certain 

 aquatic mammals, like the seals and sea-otters. There is a strong 

 sacrum of two vertebrae, however, the pelvis and hind legs being 

 connected with the spinal column firmly, clearly proving that, like 



'.An additional phalange has also been observed in the fifth toe of a South 

 American species. 



