November, 1842.] 217 



high water the sand changes its color from yellow to white, and assumes 

 a quicksand character, which it retains for one or two feet, when it is suc- 

 ceeded by a coarser and sharper sand, with the occasional occurrence of 

 thin strata of foetid black mud or clay. Small masses of marine fossil 

 shells,* lying horizontally, or nearly so, are found scattered at intervals 

 throughout this sandy formation, at almost every point of the canal. The 

 depth varies from five feet above to five feet below the line of high tides, 

 which is the greatest depth to which the excavation has extended. 



The rib and vertebra of the whale were discovered near the northern 

 extremity of the swamp, in the yellow sand, and about a foot below its sur- 

 face. They were much worn, and one of the vertebra was much incrusted 

 with barnacles. At this point bog iron ore and protophosphate of iron 

 were found above the sand containing the marine shells. 



The precise spot where the extinct Chelonia (C. Couperi of Harlan) 

 occurred was not ascertained; but there is every probability that it was 

 taken from the same formation. 



The bones of the mammalia occurred generally in groups; and in some 

 cases a large number of those of the same skeleton were found together. 

 From this circumstance and the unworn and perfect state of many of the 

 bones, it is highly probable that the carcasses of the animals were floated, 

 or fell into the then lake or stream, and that, sinking to the sandy bottom, 

 they were gradually covered to their present depth by the deposits of the 

 sediments of the water. Of the species discovered, the remains of the 

 Megatherium and the Mammoth were.the most abundant; and of the former 

 six heads of femurs were found in the bed of the canal within the distance 

 of a mile. All the bones were at the same depth, and imbedded in the 

 same stratum; thus leaving no doubt of their co-existence at a period suc- 

 ceeding the elevation from the ocean of the newer pliocene, but antece- 

 dent to the formation of the older recent alluvium of this coast. 



The co-existence of the Megatherium with the Mastodon, Mammoth, 

 Hippopotamus, Horse, Ox, and Hog, has here, it is believed, been for the 

 first time established; and forms, with the discovery on this continent, of 

 a well defined fossil species of Sus, two interesting facts in Geology. 



The identity of most of the fossil shells which were found below the 

 bones of the mammalia with the existing species on this coast, proves 

 that the temperature of the ocean, long prior to the existence of the Me- 

 gatherium, Mammoth, and Hippopotamus, was such as is congenial to the 

 present mollusca. Another inference which may be^drawn is, that the 

 surface of the country has undergone no sudden or violent change since 

 these gigantic animals occupied its forests and morasses; but that such as 

 have occurred have been slow and gradual. 



* The following species occur most abundantly: 



Venus mercenaria, Pyrula caurica, Cardium ventricosum, Artemis con- 

 centrica, Area pexata, Area ponderosa, Lucina divaricata, Modiola late- 

 ralis, Tellina alternata, Mactra lateralis ? Oliva literata, Natica duplicata, 

 Crepidula convexa. 



