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provinces of the New World. Though this boundary must be sought 
for further to the northward, we yet find in Guatemala a Sorex 
among mammals, the great mass of the Mniotiltide among birds, 
Tropidonotus and Ischnognathus among snakes, and Rana among 
frogs. 
It must not be supposed that a definite boundary line, beyond 
which the species of ezther region do not pass, can ever be drawn be- 
tween these two or any two zoological provinces. The real division 
will probably prove in this case to extend over a wide tract of coun- 
try, and to occupy a position within certain limits, which include a 
district inhabited by forms to be considered as typical of each ; the 
true boundary being that portion of such a district where the typical 
forms of each are found in equal numbers. 
In making such a comparison, it is evident that forms that are 
common to the two regions, as well as such as inhabit exclusively 
the district in question, need not be taken into consideration. Thus 
viewing the list I give below, we find the southern genera considerably 
predominating over the northern. Taking the genera of snakes 
peculiar to the south, we have Homalocranion, Tomodon, Spilotes, 
Dromicus, Ahetulla, Leptodeira, and Dipsas; while the only genera 
peculiar to the north are Ischnognathus and Tropidonotus. Those 
common to the two continents are Herpetodryas, represented by the 
northern H. flavogularis, and by the southern H. rappii, H. bod- 
daertii, and H. brunneus; and Elaps, represented by L. corallinus 
and Z. fulvius. Of these, Hlaps is hardly to be called a typical 
northern form, as it does not range far into the United States. The 
genera found in Guatemala, and not elsewhere in the Americas, are 
Streptophorus (S. sebe) and Dipsadomorphus (D. biscutatus). 
Of Batrachians, the North American genus Rana occurs, but no 
Tailed Batrachians: Bufo nebulifer is found at Duefias, Bufo agua 
in Vera Paz, Engystoma carolinense at Coban, and Rana halecina 
everywhere. Of Lizards, Basiliscus and Corythophanes occur at 
Lanquin, the former in abundance; they are also both found spa- 
ringly at Duefias. Tropidolepis and Cnemidophorus occur both at 
Duefnas and Coban. 
Again, referring to the division between the Nearctic and Neotro- 
pical regions, it appears certain that the northern forms extend far 
further to the southward along the table lands than along the hot 
districts of either seaboard ; and again, the southern forms range 
further to the northward along the coasts than along the table lands. 
In Guatemala the “tierra caliente’ seems, with very few exceptions, 
to embrace purely Neotropical types; whereas on the table lands 
and the more elevated and temperate districts only, all the North 
American genera and species that are to be found in the country 
occur. 
Besides the Snakes enumerated below, there is a Rattlesnake 
(Crotalus) found in many parts, specimens of which I did not ob- 
tain. There is alsoa Cenchris, probably C. piscivorus, a fine example 
of which was one day brought to me by an Indian ; but being too 
