218 THE BATH OOLITE PERIOD. CHAP. 



behold him wading- by his long legs, or swimming by help 

 of the tail, a gigantic triton among not inconsiderable cepha- 

 lopods, whose tough muscles he shared with the frequent voracious 

 sharks ; at other times he may have been content with the spare 

 diet of marsupial quadrupeds which lived on the borders of the 

 water. It is perhaps worthy of remark that the teeth are very 

 little or not at all worn, even toward the point ; they seem to have 

 fallen easily out of their incompletely-separated sockets, which are 

 almost united into a long groove, and to have been replaced by 

 several renewals, so that he was as well supplied with weapons as 

 the sharks, with whom, probably, he was not on good terms. 



The mixed zoological relationships which are discovered by 

 examination of the bones, offer curious and tempting problems to 

 the comparative anatomist. What is known of the succession of 

 life-forms in geological periods is enough to assure us that, in 

 every class, in many orders, and in some families and even genera, 

 there is evidence of gradual substitution of one later form for 

 another earlier, without, as far as is known, any recurrence to a 

 former stage. If we tread back those steps, we are led into no 

 labyrinth, or workshop in which Nature is found trying her ' pren- 

 tice hand / we are stopped ; there is no further progress ; the form 

 is lost ; other and earlier races appear, of which these have taken 

 the place g . 



The steps backward and forward of megalosaurus are few : the 

 lias, oolites, and wealden are the limits of his race. If we include 

 all his kindred all the deinosaurs their pedigree ascends only 

 to the midst of the poikilitic rocks, where they first appear associated 

 with a widely different group of reptiles which can be traced far 

 backward through many steps, but not any in the forward direction. 

 Among the earliest reptiles closely allied to megalosaurus may be 

 noted teratosaurus of the Keiiper, of which fine portions in the 

 British Museum might be mistaken for their later relative. 



The lengths of the head, body, and tail of megalosaurus have 

 been separately estimated by Professor Owen in his Report on 

 Fossil Reptiles (1841, p. 109), as follows : 



8 'Augescunt alise gentes, alias minuuntur, 



Inque brevi spatio mutantur ssecla animantum 

 Et, quasi cursores, vitai lampada tradunt/ 



LUCRET. ii. 76. 



