Mr. 11. (r. Soeley on Acantho[)holi.s [)laty|)u.s. '.i05 



tlu" archipelago on tli«* north wa.-< tonnerly united to the 

 southern continent, ami that it ha.>< .since been an area of .sub- 

 sidence* ; and that .sinudtaneou.sly with this subsidence was 

 created the low watershed which now separates the Amazon 

 and Caribbean waters. 



XXXVII. — On Acanthopholis platypus (Seelei/), a Piichyjyod 

 from the Camhrithje Upper Greensand. By IIarry G, 

 Seeley, F.G.tS., St. John's College, Cambridge. 



[Plate VU.] 



There is no period in English geology in which the rocks 

 themselves have not furnished evidence of the proximity of 

 land to what are now our coasts. Occasionally they prove the 

 present land and the past lands to have in part included each 

 other; and in bct%vecn these periods of similar altitude the 

 depression is rarely if ever so profound or wide-spread as to 

 remove the land to a distance too great to be measured ap- 

 proximately in miles by the evidence from the distribution of 

 its detritus. But when the stratigraphic teaching becomes 

 difficult to read or unravel in reasoning, then the fossils come 

 to hand, in a rough way cut the knot that could not be untied, 

 and invest the subject Avith new interest in the distribution of 

 life ; for sea-life, land-life, and river-life are in the main so 

 different from each other, that they give evidence of the extent 

 of strata and of the causes which limited them which are 

 second only in usefulness to the lithological and petrologic 

 facts. Among such obscure problems, but for its fossils, would 

 have been the histor}^ of the Cambridge Upper Greensand — a 

 mere junction-bed between the Gaidt and the Chalk ; but the 

 fossil fruits, the sea-birds allied to Cohjmhus and the penguins, 

 the flocks of aerial quadnipcds (Omithosaurs), the schools of 

 Emydian Chelonians, and, lastly, the land-quadruped Acan- 

 thojyJioIis, point to their home in a not distant country, of 

 which the other deposits between the Gault and Chalk to the 

 south and north help to tell the whereabouts and history. 



clay was not prominent on the Rio Xapo till we reached long. 74° and 

 an altitude of ooO feet, where there is a verj^ high bank called Puea-ureu 

 or monte Colorado, containing lignite — " nna viina de carbon de piedra,''^ 

 says Villavicencio. This interstratified lignite is traceable eastward as 

 far as Tabatinga. Darwin says that the Pampean formation was accom- 

 panied by an elovatory movement. 



* This is suggested by the South-American character of the West- 

 Indian mammals and m'ollusks. There are palreontological reasons for 

 believing (Proc. Acad. Nat. Sc. Philad. 1868, p. 313) that the Caribbean 

 continent was not submerged before the close of the Postpliocene. 



