XL STONESFIELD REPTILES. 183 



ICHTHYOSAURUS ADVENA. Phil. 



Very few remains of this marine or even pelagic genus occur 

 among the reliquiae of the littoral lagoon of Stonesfield. Only 

 vertebrae have been recorded. 



PLESIOSAURUS ERRATICUS. Phil 



A few cervical vertebrae belonging to a small species of this 

 genus have occurred at Stonesfield, and perhaps a few teeth and 

 a portion of lower jaw belong to the same. They hardly afford 

 specific characters for distinction from others which occur in the 

 oolites, but it is convenient to give a name for reference. 



TELEOSAURUS. 



Teleosaurus, a genus of mesozoic crocodiles, first made known 

 in England by the discovery of entire specimens at Whitby, is 

 not recorded in the country round Oxford in any rock older 

 than the Stonesfield beds. It is rarely mentioned at all further 

 south in England, but occurs in the oolite of Normandy. Formed 

 for aquatic motion, and associated with marine remains, its ordinary 

 way of life may be understood by analogy with the sharp-nosed 

 crocodile of St. Domingo, which ventures pretty freely out to 

 sea, more so than the crocodile of the Senegal and the Nile, the 

 caiman of America, or the gavial of the Ganges. 



Adopting the gavial for a general term of comparison, we re- 

 mark, first, the correspondence of size between the modern Eastern 

 and the old Western saurian. The gavial reaches a length of 

 fifteen or eighteen feet, and this is about the size of the largest 

 fossil yet measured. The large teleosaurus of Whitby measures fifteen 

 feet two inches, a portion of the beak wanting. Judging by the 

 breadth of the cranium (thirteen inches), the whole head has been esti- 

 mated at four feet and a half, and the entire length from the beak 

 to the end of the tail, eighteen feet. The head length assumed is 

 perhaps too great ; but as there are only thirty-three out of forty- 

 two vertebrae in the tail, the entire length may have been as 

 supposed. In the gavial the head constitutes between one-fifth 

 and one-sixth of the whole length, the tail less than one-half. The 



