338 AMERICAN CRETACEOUS ROCKS. [Ch. XVII 



south of France, Spain, Sicily, Greece, and other countries bordering 

 the Mediterranean. 



The species called Hippurites organisans (fig. 329) is more abun- 

 dant than any other in the south of Europe ; and the geologist should 

 make himself well acquainted with the cast d, which is far more com- 

 mon in many compact marbles of the Upper Cretaceous period than 

 the shell itself, this having often wholly disappeared. The flutings, 

 or smooth, rounded, longitudinal ribs, representing the form of the 

 interior, are wholly unlike the Hippurite itself, and in some individu- 

 als attain a great size and length. 



Between the region of chalk last mentioned, in which Perigueux 

 is situated, and the Pyrenees, the space B intervenes. (See Map, fig. 

 326.) Here the tertiary strata cover, and for the most part conceal, 

 the cretaceous rocks, except in some spots where they have been laid 

 open by the denudation of the newer formations. In these places 

 they are seen still preserving the form of a white chalky rock, which 

 is charged in part with grains of greensand. Even as far south as 

 Tercis, on the Adour, near Dax, cretaceous rocks retain this charac- 

 ter. I examined them in 1828, and M. Grateloup found in them 

 Ananckytes ovata (fig. 287, p. 325), and other fossils of the English 

 chalk, together with Hippurites. 



CRETACEOUS ROCKS IN THE UNITED STATES. 



If we pass to the American continent, we find in the State of New 

 Jersey a series of sandy and argillaceous beds wholly unlike our 

 Upper Cretaceous system ; which we can, nevertheless, recognize as 

 referable, palseontologieally, to the same division* 



That they were about the same age generally as the European 

 chalk and greensand, was the conclusion to which Dr. Morton and 

 Mr. Conrad came after their investigation of the fossils in 1834. The 

 strata consist chiefly of greensand and green marl, with an overlying 

 coralline limestone of a pale yellow color, and the fossils, on the 

 whole, agree most nearly with those of the Upper European series, 

 from the Maestricht beds to the gault inclusive. I collected sixty 

 shells from the New Jersey deposits in 1841, five of which were iden- 

 tical with European species — Ostrea larva, 0. vesicularis, Gryph&a 

 costata, Pecten quinque-costatus, Belemnites mucronatus. As some of 

 these have the greatest vertical range in Europe, they might be ex- 

 pected more than any others to recur in distant parts of the globe. 

 Even where the species were different, the generic forms, such as the 

 Baculite and certain sections of Ammonites, as also the Inoceramus 

 (see above, fig. 308, p. 328), and other bivalves, have a decidedly cre- 

 taceous aspect. Fifteen out of the sixty shells above alluded to were 

 regarded by Professor Forbes as good geographical representatives of 

 well-known cretaceous fossils of Europe. The correspondence, there- 



