MAMMALS 



473 



is called Archaopteryx (Fig. 158), and has many points of resem- 

 blance to the reptiles, and many characters which recur only in 

 the embryos of modern birds. The peculiarities which strike one 

 at the first glance are the head and tail; there was no horny 

 beak, but the jaws are set with a row of small teeth, while the tail 

 is very long, composed of separate vertebrae, and with a pair of 

 quill feathers attached to each joint. The wing is constructed on 

 the same plan as that of a modern bird, but is decidedly more 

 primitive. The four fingers are 

 all free (in recent birds two of 

 them are fused together) ; they 

 have the same number of joints 

 as in the lizards, and are all 

 provided with claws. The plu- 

 mage is thoroughly bird-like in 

 character, but is peculiar in the 

 presence of quill feathers on the 

 legs. This very extraordinary 

 creature was, then, a true bird, 

 but had retained many features 

 of its reptilian ancestry, and 

 shows us that those ancestors 

 have still to be sought in the 

 Trias or even the Permian. 



Mammalia. — The mammals 

 of the Jurassic are still very rare 

 and imperfectly known, and have been found in only a few places. 

 How many mammalian genera should be referred to the Jurassic 

 will depend upon where the somewhat arbitrary line is drawn, 

 which separates that system from the Cretaceous. Excluding the 

 transition beds of Wyoming and the Purbeck of England, three 

 genera are known from the Jura, all found in European localities : 

 Phascolotherium, Amphitherium, and Stereognathus, all of them 

 tiny and very primitive creatures. From the scanty remains it is 

 not possible to learn much about them. 



FIG. 158. — Restoration of Archceopteryx 

 macrura. (Andreae.) 



