244 ON MEXICAN AMPHIBIANS AND REPTILES. [June 6, 
Unless this conclusion be accepted, we have to resort to violent 
interpretations. Hither complete extinction all over North 
America, a measure which receives no support from actual 
distribution; or we must be prepared to assign to the 
Opisthoglypha a Cretaceous age, as a family not descended from 
North-American Colubrine ; or, lastly, if we should insist upon 
the Opisthoglypha as a natural group, the only explanation 
would be a land-connection across the Equatorial Atlantic, which 
with shifting modifications is supposed to have existed from 
Lower or Mid-Cretaceous into at least the Oligocene epoch. 
This bridging of the Atlantic is somewhat problematic. For 
our purposes we can discard the Cretaceous Brazil—Africa con- 
nection. Of more concern to periaretic distribution is the Europe— 
Greenland—North America continuity, which is supposed to have 
persisted well into the Tertiary period. But there was a third, more 
direct. bridge, although one of a curious and mysterious structure, 
which by its several advocates is dimly described as composed of 
a shallow sea interspersed with many islands; or as a solid land- 
belt; or, lastly, as a long archipelago with a continuous coast. 
This mysterious structure is supposed to account for the 
unmistakable similarity between the now extinct Antillean and 
Mediterranean coral-fauna, Old- World and Antillean land-mollusea, 
de. Obviously the corals require sea, the mollusca land. The 
apparent contradiction may be solved by the suggestion that 
there existed between Central America and the Mediterranean 
a sea (part of the Tethys of Suess and Ortmann, later their “ Great 
Mediterranean”), shallow during the Oligocene epoch, studded 
with islands, bordered by continuous land in the South (Brazilia 
to West Africa, or later between N. South America and West 
Africa, part of the Mesozonia of Ortmann) and in the North 
(Western Europe to Appalachia). Subsequently the Tethys 
increased to a big “bay” in Mid-Atlantic, this bay extending, 
spreading south and north, drowning first the southern land-belt, 
driving the northern land farther and farther north, with the 
ultimate result of a junction of the South with the North 
Atlantic; in other words, establishment of the whole Atlantic, 
Now these land-bridges, provided they existed long enough and 
at the right time and place, the Southern until at least the 
beginning of the Eocene, the Northern at least through the Oligocene 
epoch, would explain many a puzzle in geographical distribution ; 
for instance, that of the Aglossa, Boas, Podoenemis, Amphis- 
benide, Solenodon. The Northern bridge would throw light 
upon the Anguide and upon Spelerpes, a large American genus 
with a solitary species in Sardinia and Italy. 
But this is at present a land of dreams. With more claim to 
reality, we can conclude that Central America, although genetically 
part of the North-American continent, has received vis dominant, most 
characteristic fauna from South America, and this southern fauna 
has surged northwards chiefly to the east and west of the 
Mexican plateau. 
