Ch. XVI.] EOCENE STRATA IN UNITED STATES. 233 



but in parts very compact and calcareous. It contains several peculiar 

 corals, and a large Nautilus allied to iV. zicsac ; also in its upper bed a 

 gigantic cetacean, called Zeuglodon by Owen.* 



Fig. 246. 



Zeuglodon cetoides, Owen. 

 fiasilosaurus, Harlan. 

 Fig. 245. Molar tooth, natural size. Fig. 246. Vertebra, reduced. 



The colossal bones of this cetacean are so plentiful in the interior of 

 Clarke County as to be characteristic of the formation. The vertebral 

 column of one skeleton found by Dr. Buckley at a spot visited by me, 

 extended to the length of nearly 70 feet, and not far off part of another 

 backbone nearly 50 feet long was dug up. I obtained evidence, during 

 a short excursion, of so many localities of this fossil animal within a dis- 

 tance of 10 miles, as to lead me to conclude that they must have belonged 

 to at least forty distinct individuals. 



Prof. Owen first pointed out that this huge animal was not reptilian, 

 since each tooth was furnished with double roots (see fig. 245), implanted 

 in corresponding double sockets ; and his opinion of the cetacean nature 

 of the fossil was afterwards confirmed by Dr. Wyman and Dr. It. W. 

 Gibbes. That it was an extinct mammal of the whale tribe has since 

 been placed beyond all doubt by the discovery of the entire skull of an- 

 other fossil species of the same family, having the double occipital con- 

 dyles only met with in mammals, and the convoluted tympanic bones 

 which are characteristic of cetaceans. 



Near the junction of No. 2 and the incumbent limestone, No. 3, next 

 to be mentioned, are strata characterized by the following shells : Spon- 

 dylus dumosus (Plagiostoma dumosum, Morton,) Pecten Poulsoni, Pecten 

 perplanus, and Ostrea cretacea. 



No. 3 (fig. 244) is a white limestone, for the most part made up of the 

 Orbitoides of D'Orbigny before mentioned (p. 232), formerly supposed 

 to be a nunimulite, and called N. Mantelli, mixed with a few lunulites, 

 some small corals, and shells.f The origin, therefore, of this cream- 

 colored soft stone, like that of our white chalk, which it much resembles, 

 is, I believe, due to the decomposition of these foraminifera. The surface of 

 the country where it prevails is sometimes marked by the absence of wood, 



* See Memoir by R. "W. Gibbes, Journ. of Acad. Nat. Sci. Philad. vol. i. 184*7. 

 f Lyell, Quart. Journ. GeoL Soc. 1847, voL iv. p. 15. 



