INSTITUTE OF SCIENCE, PHILADELPHIA. 11 



country, and its absence constituted one of the negative faunal features 

 by which the American Tertiary formations were distinguished from the 

 European. The discovery of a true Cerithium rock, therefore, becomes 

 an interesting feature in connection with the geology of this region. 



The country about here presents the appearance of an inhospitable 

 sand tract, thinly dotted with pine groves, and covered with a low 

 growth of saw-palmetto (Sabnl scrm/a/a), the reputed home of the 

 rattlesnake and moccasin. We found a species of prickly-pear (Opnntia) 

 in bloom. A short piece above Ballast Point proper, at Newman's Land- 

 ing, is the outcrop which furnishes the silicified shells and chalcedonized 

 corals to which reference has already been made. Unfortunately, the 

 position of the outcrop is such as not to permit of an absolute correlation 

 with the deposits exposed at the Point, but I feel satisfied that it cannot 

 represent an age very different from that of the yellow limestone, with 

 which it holds several molluscan species in common. Its position is in 

 the Lower Miocene scries. The greater number of the species are here 

 imbedded in a marly matrix, from which they can be readily removed by 

 means of a pick or mattock. With few exceptions all the forms are extinct ; 

 a limited number of them are found in the nearly equivalent deposits of 

 the island of Santo Domingo. The corals are principally astraeas and 

 madrepores, but of a number of distinct species; as far as could be deter- 

 mined they form a border fringe, the remains possibly of an ancient reef. 

 What led to their hollowing out in the form of geodes, and the manner of 

 the substitution of chalcedony for the carbonate of lime, are problems still 

 awaiting solution ; doubtless, heated waters, largely impregnated with 

 silica, were directly involved in the operation, but just why the outer layers 

 of the coral masses should have been preserved, while the inner parts so 

 readily yielded to solution, is not exactly apparent. 



The day after our arrival in Tampa, I, in company with our cook, 

 made an examination of the lower Hillsboro, sailing up the river in 

 our skiff for a distance of about five miles. The shores were almost 

 everywhere very low, rarely rising more than five or six, or a dozen, feet 

 above the water, except immediately above the town, where, a short dis- 

 tance from the left bank, there is a somewhat abrupt rise of possibly 

 twenty feet or more. A fairly luxuriant growth of woodland covers 

 both banks for the greater distance, but we found few traces of that 

 primeval forest which at one time, doubtless, graced this region as it 

 still does the region of the Checshowiska. Nor did the forest present 

 here the same tropical appearance which it unfolds in the region further 

 to the north ; the bay and water-oak still continue as some of its dom- 

 inating features, but there is a very noticeable deficiency of palmettos, 

 and, in their stead, a marked increase of the coniferous element yellow- 

 pine and swamp cypress. 



