REPTILES ABUNDANT. 77 



derives its name from the approximation to the whale tribes 

 seen in the form of its vertebras. In this group there is a 

 genus presenting ball-and-socket vertebrae, and thus proving 

 its advanced character ; but, strange to say, the concavity is in 

 this case directed backwards, instead of forwards, which is the 

 universal arrangement in similar cases in our era. 



[Overlooking two molar teeth from between the keuper and 

 lias, and some remains from the Upper Trias, at Frome, in 

 Somersetshire, the Oolite formation is now (1860) to be con- 

 sidered as the era of the first appearance of mammalian life. 

 From the Stonesfield slate, situated between the Inferior and 

 Great Oolite, we were presented many years ago with several 

 specimens of the jaw-bone of a quadruped (Phascolotherium 

 BucUandii) evidently insectivorous, and inferred, from pecu- 

 liarities of structure, to have belonged to the marsupial order 

 (pouched animals), 1 of which no examples now reside on the 



FIG. 58. 



Lower Jaw of Phascolotherium Bucklandii. 



elder continent. Very recently, the Purbeck beds, a little 

 higher in the scale, have- given forth what might be called an 

 abundance of mammalian remains, though chiefly lower jaws, 

 and these have all been with tolerable confidence referred to 

 marsupials, insectivores, and rodents orders whose inferior 

 organization makes their conspicuousness at so early a period 

 highly significant.] 



The highest part of the oolitic formation presents some 

 phenomena of an unusual and interesting character, which 

 demand special notice. Immediately above the upper oolitic 

 group in Buckinghamshire, in the vicinity of Weymouth, and 



1 Fragments attributed to a cetaceous animal, another humble form 

 of the mammal class, have likewise been found in the great oolite, near 

 Oxford. 



