458 JENKINS— GEOLOGY OF THE [May 29, 



now living, most of which also live on the Brazilian coast. The Pecten may 

 also be, but we don't happen to have it." 



All the rest of the shells are West Indian forms now living. The age 

 of the deposit is probably late Quaternary. The deposit is evidently estu- 

 arine, the sea having extended into the old river channel in a narrow embay- 

 ment. The water was mostly salt, but partly brackish, for Bulla, Cerithium, 

 Neritina, Corbula, Ostrea, and possibly Area (making a total of nine species 

 out of twenty-two) are brackish water forms. Neritina virginca is some- 

 times found even in practically fresh water. 



Log of a Well at Natal, Rio Grande do Norte. 



(Reported by R. H. Soper in a letter of Sept. 21-29, 1912, to J. C. Branner.) 



" I give here the log of a well which was drilled about one mile 

 [two kilometers] from the bridge, toward Natal, across the river 

 from Natal, and on the low marshy ground which borders the 

 stream. The figures are from Burgess, the driller whom you may 

 remember as the German who drilled the well in the crystalline stuff 

 at Baixa Verde. He kept samples systematically which I saw and 

 from which I compiled this record. 



Meters. 



0-32 All a blackish, sandy, sticky, clayey mud. All contains more or 



less water which is salty. 

 32-41 A sandy cla}-, mixed with pebbles and boulders of quartzite. The 



largest pebble in the sample was about the size of a hen's egg. 

 41-42 White fine-grained sandstone. 

 42-44 Yellowish brown, clayey sandstone. 

 44-46 Whitish clayey sandstone. 

 46-50 Fine-grained reddish sandstone with occasional large pebbles of 



quartzite. 

 50-55 Dark, fine-grained sandstone with some clay and a little mica. 

 55-57 Quartzite pebbles with chunks of a mineral which gives a sharp 



biting taste like sal ammoniac. 

 57-64 Dark colored fine-grained sandstone which gives place to a hard, 



coarse-grained sandstone. 

 64-67 Dark pebbles of quartzite with pieces of hard, coarse-grained, 



vitrified sandstone. 

 67-82 A very fine-grained sandstone with considerable clay. Very hard. 



Comes out wet and black. Is a grayish white when dry. 

 82-87 A hard, brownish, sandy clay. When wet it was very black and 



could only be removed from hands with kerosene. Had a bad 



smell. 

 87-88 Same as 67-82. 

 88-94 Same as 82-87. 



