OCR Text |
Show 1 9 0 5 .] AMPHIBIANS AND REPTILES. 205 rnatina? point to the long-continuecl land-connection with Eastern Asia. A later centre of dispersal lies in the Eastern half of North America, the old Appalachia, the Alleghany mountains, &c., whence Urodeles have spread, as Plethodontinse and Desmognathinse, over most of the Eastern and Southern States, also into and through Mexico's eastern half. This spreading dates back to Miocene times, witness the existence of Spelerpes in Hayti, while others have reached even South America, and, lastly, the occurrence of a Plethodon somewhere in the La Plata basin. Much later immigrants, directly from the old north-western home, are Amblystoma and Batrachoseps : A. tigrinvm and B. attenuatus being identical species in the States and in Mexico, only A. alta-mirani being a new modification; while Spelerpes has developed many species, different in the north, centre, south, and in Hayti. A n u r a . P e l o b a t iDj® .-Scaphiopus, the Spadefoot, closely allied to the European Pelobates, is the only American genus of this family, with about 7 or 8 species, two of which are restricted to the United States. The zone of sandy terrain of Texas, New Mexico, and California is richest in Spadefeet, whence they have extended over the Mexican plateau down to the Pacific and Atlantic coasts. S. dugesi s. hammondi has the widest distribution : from Missouri and California through New Mexico and Texas, the mountains west of Chihuahua, in Guanajuato, and again on the southern slope of Oaxaca, where I found it at Totolapan, its most southern locality. The retiring habits of the Spadefoot no doubt account for the few scattered records. The well-wooded mountain ranges which form the south-eastern, southern, and western borders of the Mexican plateau are a natural obstacle to a further southward spreading of this genus. B u f o n id ^e .-Central America and Mexico are one of the centres of Bufonidte. Concerning Mexicans, they can be grouped as follows:- 1. Indigenous: Rhinophryne dorsalis, the only species of the genus, a toad specialised as an eater of Termites ; it is restricted to the moist Atlantic Tierra Caliente, from Tuxpan, north of Vera Cruz, through the Isthmus to Campeche and Guatemala. The light-coloured spots on the bluish-slaty black skin are either yellow or orange to red, varying in individuals from the same locality. They are very sluggish, rather nocturnal, and retire beneath a rotten stump or into a small self-dug hole in the moist humus. Aztec name " Poclie." 2. Southerners : Engystomops, the few species of which range from Venezuela and Ecuador northwards, but only E. jmstulosus reaches the Isthmus of Tehuantepec. Several of the 13 species of Bufo found in Mexico are southern forms : in their spread northwards they either stop short at the |