FISHES OF CEARA, BRAZIL JORDAX AND BRANNER 3 



east they form, in part at least, the flat-topped mountains of the 

 western and southern boundaries of the State of Ceara. 



The section across the Serra do Araripe given herewith has been 

 constructed from the notes of Gardner and Capanema : 



Sandstone forming the top of the mountain, 140 feet (Capanema). 

 Sandstone series, yellow, white, and red, 600 feet (Gardner) ; (this includes 

 the top bed of Capanema). 



Thin-bedded limestone (thickness not stated). 



Lignite, 2 feet (Gardner) ; bituminous shale (Capanema). 



Blue clay and gray sandstone at base (Capanema). 



The sequence, character, and relations of the rocks in the Serra do 

 Araripe are sufficiently clear from this section to render further ver- 

 bal description unnecessary. 



The fishes have only been found in concretions, and are said to 

 come from the sandstone bed above the limestone layer. They have 

 never been found in place, but occur in the talus and soil on slopes at 

 the base of the sandstone ridges. The ijiatrix in which the fossils 

 occur is mostly the buff or cream-colored limestone in which these 

 fossils have hitherto been found. 



The rock matrix suggests that w^hile some of the specimens are 

 from sandstone beds, most of them are from beds, or at least from 

 lenses, of limestone. 



Slides were made of the matrix of two of the concretions. Under 

 the microscope it is seen that the bulk of the rock is composed of 

 microscopic crystals of calcite somewhat stained with iron. The cal- 

 cite crystals, however, are so small that they are scarcely distin- 

 guishable, even under an enlargement of 90 diameters. Between 

 5 and 10 per cent of the rock is made up of clear round calcite bodies 

 evidently of organic origin. 



. Fragments were broken from specimens in the Rocha Collection 

 and chemical analyses were made of them with the following re- 

 sults. Care was taken not to include parts of the fossil fishes in the 

 pieces analyzed. 



Analysis of pieces of a fossil-bearing concretion from Ccard, Brazil 



L. R. Lenox, Analyst 



(Record Book 779) 



Silica (SiOs) 3.64 



Oxides of iron and alumina ( AI2O3 FcsOa) i .46 



Lime (CaO) 52.23 



Magnesia (MgO) 0.56 



Loss in ignition (CO2, H2O, etc.) 42.28 



Total 100. 17 



