30 REPTILES 



culty, while, in the second place, if this were accomplished, it 

 would be quite valueless. It would be difficult because the 

 records are much scattered, and a number of generic and specific 

 names have been assigned to specimens of so imperfect and 

 unsatisfactory a nature that in many cases it is impossible 

 to say whether or no they are mere synonyms. It would be 

 valueless because the known forms of extinct reptiles must, from 

 the very nature of the case, bear but a small proportion to the 

 number of species that have existed. Nor is this all, for in order 

 to make the census of the slightest use it would be necessary to 

 divide these known forms into time-horizons, the number of 

 which it would be extremely difficult to fix satisfactorily. 



Neither, in the present state of zoological science, is a 

 census of the existing members of the class altogether free from 

 some degree of uncertainty ; for very different views of the 

 limitations of species are entertained by different naturalists. 

 In accepting, however, the number of species given in the 

 volumes of the British Museum Catalogues we shall certainly 

 be on the safe side, as the author of the latest editions of such 

 of those works as deal with reptiles is a naturalist who takes a 

 broad view of the limitations of a species, and is not given to 

 hair-splitting in this respect. It must be remembered, however, 

 that these works are now somewhat out of date in respect to 

 the number of known species of reptiles, the last volume of the 

 catalogue of lizards having been published so long ago as 1887, 

 while the one on crocodiles and chelonians was issued a year 

 later, and the concluding volume of the snake-catalogue in 

 1896. 



Taking, however, the data given in these volumes, we have 

 the following numbers for the five chief divisions of existing 

 reptiles, namely : — 



Tuateras (Rhynchocephalia) 

 Crocodiles (Crocodilia) 

 Tortoises and Turtles (Chelonia) 

 Lizards (Lacertilia) 

 Snakes (Ophidia) 



1 



23 



201 



1616 



1639 



This gives a total of 2480 species, a number which, by subse- 

 quent additions to the list, may be safely increased to at least 

 2600. 



