20 



mingled with Ostrea Virginica occupy the highest place. But gene- 

 rally, the same shell re-appears as a predominant constituent of one 

 or more of the subjacent beds ; and such is the diversity of ar- 

 rangement, even to places but a few miles distant, that it is obvious 

 that no general order of succession exists. Thus, in a range of 

 three miles we find Perna maxillata in some localities in the lowest 

 stratum of dark blue argillaceous sand ; in others, forming an 

 upper, or even the highest layer of the series. At Waller's mill, 

 three miles from Williamsburg, this fossil overlies the other shells ; 

 whereas at the College mill, as already stated, it forms a part of 

 the lowest visible stratum. 



With the view of conveying more precise ideas of the disposition 

 of the fossils in this region, we annex the following details in relation 

 to some of the more important localities, which have been minutely 

 examined. 



King's mill, one of the most interesting fossil localities in the 

 neighbourhood of Williamsburg, is situated on the north bank of 

 James river, about twenty-five miles from its mouth. The cliff in 

 which the shells appear is abrupt, and has a height varying from 

 twenty to forty-five feet above the water. The strata of shells 

 extend along the river with slight interruptions, when the cliff sinks 

 nearly to the level of the water, for a distance of between two and 

 three miles, and they' are found in a somewhat similar order of 

 superposition for some distance inland. Their general direction is 

 horizontal, but the outline of any one stratum is frequently very 

 irregular, the surface rising and falling with a steep inclination. 

 This irregular outline is particularly remarkable with the beds of 

 Chama, which are very thick at some points, and then fine out 

 rapidly and again expand. 



This deposite of shells is covered to the depth of from four to six 

 feet by a brownish yellow sand, intermixed with stripes of clay. 

 Beneath this is a thin layer of about one foot, of very argillaceous 

 and ferruginous clay of a red colour. This rests upon a few inches 

 thickness of gravel, consisting of water-worn quartz, rarely larger 

 than a pea. Beneath this is a layer, from one to two feet thick, 

 consisting of yellow sand, containing a great deal of the green or 

 chloritic sand, arranged in narrow stripes. Next follows a layer of 

 the same sand, containing principally Chama and Venus deformis. 

 This is from two to three feet in thickness. Immediately below is a 

 stratum consisting almost exclusively of Chama, with a few Area 



