448 JENKINS— GEOLOGY OF THE [May 29, 



Desterro. 



On the northern side of the broad valley of Potengy, north of 

 Macahyba and near the place of Desterro, are some surface indica- 

 tions of limestone. Holes, a meter in depth, have been dug in pros- 

 pecting for limestone. The material in these dug-outs is a yellow 

 sandy limestone containing fossils, evidently in the same series as the 

 other limestones. 



Alvoredo. 



On the southern side of the valley of Potengy, near Alvoredo 

 and north of Macahyba, where the river cuts into its bank, is an 

 exposure of about eight meters of limestone beds. These are hori- 

 zontal. The material is the same as in the other localities with more 

 sand and with more fossil impressions. Up the river, thirty meters 

 or so, is a granite mass in place, standing about five meters high. 

 Although bushes and soil hide the actual contact of the limestones 

 with the granite, yet it was clear that the beds lapped directly on 

 top of the crystalline rocks. 



Fossils from the Limestones in the Region About Natal, 

 Rio Grande do Norte, 



The material collected from the fossil localities of the limestones 

 in the region about Natal, Rio Grande do Norte, is exceedingly 

 poor. Only casts and impressions could be found. In all they con- 

 sisted of about a dozen different species of marine or brackish water 

 shells, one questionable crustacean, and some plants, chiefly palm 

 leaves. The limestones contained, in most cases, just enough sand 

 grains to ruin the detailed character of the impressions. There 

 were no definite horizon-marking fossils, but they all have the gen- 

 eral appearance of being Tertiary, probably in the lower part of 

 the series.- 



2 A collection of the fossils from the Rio Grande do Norte limestones 

 was sent to Professor Gilbert D. Harris, of Cornell University, for examina- 

 tion, and he writes as follows of it under date of December 20, 1912 : " Many 

 of your specimens I judge belong to undescribed forms. Of the generic 

 types I see none that might not possibly be anywhere from Cretaceous to 

 recent, except perhaps the fragmentary impress of an Area. None appear to 



