EVOLUTION AND GEOLOGICAL HISTORY 173 



fresh-water Molluscs and Crustacea, such as Paludina and 

 Cypris ; they also contain remains of terrestrial plants and of 

 Iguanodon, a terrestrial reptile. In the Wealden strata of 

 Belgium has been found one little skeleton named Hylceobatra- 

 chus croyi which belongs to the Amphibia ; it is in all proba- 

 bility directly ancestral to some of the existing Urodela, 

 resembling the Proteidae except that it has maxillary bones and 

 five toes on the hind limb. In the later strata of the Cretaceous 

 series, mostly marine, no remains of Amphibia have been 

 found. In the Oligocene of France, intermediate between the 

 Eocene and Miocene, mere fragments described as Megalotriton 

 occur, and in the lower Miocene other fragments have been 

 found which seem to belong to the genus Triton. In the 

 Upper Miocene of Oeningen in Switzerland was found the 

 celebrated Andrias sclienchzeri, an almost complete skeleton 

 about three feet in length described in 1726 by its discoverer 

 Scheuchzer as 'homo diluvii testis,' the man who witnessed the 

 deluge. Cuvier recognised this skeleton as that of some large 

 newt, and modern palaeontologists have ascertained that it is 

 scarcely to be separated from the genus Cryptobranchus now 

 existing in America and Japan. The existing common newt, 

 Triton cristatus, has been identified in the Norfolk forest-bed 

 which is earlier than the oldest deposits of the glacial period. 



Palaeontology affords no more light upon the evolution of 

 the leaping Batrachia than on other difficult problems connected 

 with the Amphibia. Intermediate forms, between the Urodela 

 and the Anura, though they must have once existed, have not 

 yet been discovered. Of fossil forms one of the best known is 

 PalcBobatrachus which occurs in the Lower Miocene ; numerous 

 specimens have been obtained and more than a dozen species 

 distinguished. This genus is allied to the Aglossa, which have 

 some primitive characters, but in many others are very highly 

 specialised. The typical forms Rana and Bufo have been dis- 

 covered in the Upper Eocene and the earliest representatives of 

 the Anura are still to be sought in formations earlier than this. 



It will be seen then that the geological record, imperfect as 

 it is in many respects, seems to contradict one conclusion which 

 was formerly generally accepted, namely that the most primi- 

 tive Amphibia are those which retain their gills or gill-clefts 

 throughout life, It is now evident that the retention of the 



