26 On the Affinity of the North- American Lizard-Fauna. 



the paper — that the North-American Lacertilian fauna proper 

 is quite distinct from the South-American, and that a tran- 

 sition-fauna, leaning towards the Neotropical, exists on the 

 border-land of the two realms. This transition-fauna is 

 characterized by the large development of the Neotropical 

 family Iguanidaj, whose representatives, however, belong not 

 to South-American genera, but to genera [Phrynosoma, Scelo- 

 porus) whose species are almost exclusively restricted to the 

 transirion-tract in question and to a comparatively insignifi- 

 cant region lying immediately north and south of it. The 

 number of species that transgress these boundaries is limited, 

 although a very few go considerably beyond them. None of 

 the species of Sceloporus, which, according to Boulenger's 

 catalogue, numbers some twenty-five species, has a range 

 extending south beyond Costa Rica, and of but few does the 

 range extend beyond Mexico and Guatemala. Similarly, 

 none of the species of Phrynosoma, of which there are enume- 

 rated some twelve species, penetrate beyond Mexico. Neither 

 of these two genera, therefore, can be said to be Neotropical, 

 nor can they any more be considered to be Nearctic (Hol- 

 arctic), since the number of forms penetrating much beyond 

 the transition- tract above referred to — transitional in other 

 respects beyond what is indicated by the Lacertilian fauna 

 alone — is extremely limited. The peculiar Iguanoid forms, 

 then, are largely distinctive of the transition-tract, whose 

 fauna they serve to characterize. 



Removing this element from the North-American Lacer- 

 tilian fauna, we have remaining only some twenty species, of 

 which, as I have shown, thirteen belong to the genus Eumeces. 

 Mr. Boulenger objects to Eumeces being considered an Old- 

 World genus ; but surely it is a genus largely developed in 

 the Old World, and one that is practically excluded from the 

 Neotropical fauna. In his most recent catalogue Boulenger 

 recognizes some thirty-one species, of which thirteen belong 

 to the United States, eight are Mexican, eight Eur-Asiatic, 

 one African, and one insular (Bermudas). The range of no 

 western species extends further south than Campeche. These 

 being the facts, does not the genus Eumeces in the North- 

 American fauna indicate a distinct relationship with the fauna 

 of the Old World (Eur-Asiatic) ? Surely it indicates no 

 afiinity with the South-American (Neotropical) fauna. Fur- 

 thermore, the most broadly distributed North-American 

 Eumeces [E. fasciatus) is a form most nearly related to an 

 Asiatic species {E. marginatus, Japan), with which, indeed, 

 it has generally been united. What^ then, are the features 

 wliich unite the North-American fauna with the South- 



