Lisboa — Permian Geology of Northern Brazil. 435 



east and west of Therezina, usually argillaceous, but always 

 containing the pisolitic sandstone, passing in some places to a 

 true clay, called taud by the inhabitants of the region. 



The Psaronius from Livramento was found in a cultivated 

 field among the surface pebbles, already detached from the 

 rock, which is here a very clayey and friable sandstone. An 

 examination of the escarpments of the surrounding elevations 

 showed that they were formed of the same red sandstone. 

 Psaronius was also collected from red sandstone in the Balsas 

 river in the extreme south of Maranhao ; in Carolina, and in 

 the lowlands of the Tocantins, and, according to the notes of 

 Baumann, in the Manoel Alves Pequeno and Manoel Alves 

 Grande rivers in Goyaz, and at Porto Nacional west of the 

 Tocantins. 



Pisolitic rock. — A characteristic feature of the Permian 

 sediments is the common occurrence of a pisolitic rock. This 

 was first noticed in Biachao Fundo, near the " grota do Men- 

 des " at the contact of an overlying ashy gray sandstone with 

 the Jaboti sandstone. There the two sandstones are separated 

 by thin flinty beds, light in weight, chocolate-colored and with 

 seed-like grains. This rock seems to be derived from the 

 alteration of a pisolitic limestone whose carbonate of lime has 

 almost completely disappeared. As a rule, however, the piso- 

 litic rock is a hard white sandstone irregularly interbedded in 

 the Jaboti red sandstone. 



S. Bartholomeu sandstone. — The S. Bartholomeu sandstone 

 is ashy gray, in places friable, in others it is hard or glassy, 

 and quite commonly false-bedded. It was seen near the little 

 river of S. Bartholomeu, not far from a locality where Psaro- 

 nius was found. It occurs along the road from Pastos-Bons to 

 Biachao Fundo, where it has a thickness of about fifty meters. 



The Pastos-Bons heels. — The gray sandstone of S. Bartholo- 

 meu is overlaid by a series of rocks, generally green and choco- 

 late-colored in alternating layers, and made up of shales and 

 white calcareous layers with an intercalated white sandstone. 



These beds were first seen in the vicinity of Pastos Bons, 

 and they are well exposed in the neighborhood of that city in 

 the beds of streams draining into the Parnahyba. 



The limestones of the series are rather thin and contain 

 many layers of opal, and, like the shales, they are alternately 

 chocolate-colored and green. On top of these beds the lime 

 rock is thicker and is well exposed at the colony of G-angorra 

 near Pastos Bons, where they have a thickness of three meters 

 and are of a beautiful green color. Without doubt this is the 

 same thin limerock that outcrops at different places in the 

 Parnahyba basin. 



There is a limestone with this same thickness of three meters 



