244 ox BIEXICAX AMPHIBIAXS AXD REPTILES. [June 6, 



Unless this conclusion be accepted, we have to resort to violent 

 interpretations. Either 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 Colubrinee ; 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 periarctic distribution is the Europe- 

 Greenland-North America continuity, which is suf)posed 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-mollusca, 

 &c. Obviously the corals require sea, the mollusca land. The 

 apparent contradiction may be solved by the suggestion that 

 there existed between Centi-al America and the Mediterranean 

 a sea (part of the Tethys of Suess and Ortmann, later their " Great 

 Meditex-ranean "), 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, di-owning 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 geogTaphical distribution ; 

 for instance, that of the Agiossa, Boas, Podocnemis, Amphis- 

 bfenidee, Solenodon. The Noi-thern bridge would throw light 

 upon the Anguidpe and upon Speler2)es, a large American genus 

 with a solitaiy species in Sai'dinia and Italy. 



But this is at present a land of dreams. With more claim to 

 reality, we can conclude that Central America, although genetically 

 fart of the North- American continent, has received its dominant, most 

 characteristic fa%ma frora South America, and this southern fauna 

 has surged northwards chiefly to the east and west of the 

 Mexican plateau. 



