J. E. Todd — On Sectarian structure. 361 



conglomerate, but, for want of opportunity, they have not been 

 closely examined. 



Pitanga Station Cutting. 



This cutting is figured and described in Hartt's Geology and Physical 

 Geography of Brazil, p. 368. The pink and white shale marked g 

 has been found to contain several species of molluscs, some of which 

 have not yet been found elsewhere. Specimens of these, not well 

 preserved, are in the British Museum (Nat. Hist.), South Kensington. 

 These strata are well worthy of further exploration. The contour of 

 the cutting has been altered in late years. 



EXPLANATION OF SKETCH-MAP (p. 360). 



— > Indicating direction of dip of Cretaceous rocks as seen on the coast. 



1. Exposures of recent Raised Beach. 



2. Eemains of reptiles and fishes, usually associated with Entomostraca and 

 molluscan shells. 



3. Quarry with numerous reptilian remains and fish-scales. 



4. At Setiibal Point teeth of crocodiles are numerous, with small teeth and 

 scales of fishes, and Paludina. 



5. In the shales, limestones, and conglomerates between Escada and Plata- 

 forma numerous remains of reptiles (Crocodilia, Dinosauria, and Plesiosauria) 

 and fishes {Matvsoilia, Lepidotus, Belonostomus, Diploniystus, Chiromystus, 

 Acrodus), with numerous molluscan shells and badly preserved Entomostraca. 



6. In a high cliff a rich bone-bed with well-preserved fish-remains. 



7. In the shales and limestones between Pedra Furada and Montserrat 

 numerous remains of reptiles and fishes associated with molluscan shells and 

 Entomostraca. A Pterosaurian tooth found here. Eemains of reptiles and 

 fishes also in the conglomerate at Montserrat. 



8. In an inlet at km. 4, shale with Entomostraca and fish-remains (Mega- 

 lurus, etc.) was met with. 



VI. — More about Septarian Stktjciuke. 



By J. E. Todd, M.A., Assistant Prof essor of Geology and Mineralogy, 

 University of Kansas. 



IN his article on septarian structure in the March number of the 

 Geological Magazine Dr. A. Morley Davies seems to call for 

 further light upon the subject, hence the following is ofPered. The 

 writer became convinced of the fallacy of the current teaching 

 concerning the formation of concretions with cracked interiors and of 

 septaria more than thirty years ago, and has so taught in his classes 

 ever since. In 1902 he published a paper on " Concretions and 

 their Geological Effects 'V which presented facts which virtually 

 demonstrate that the cracking is due to the expansion of the exterior 

 rather than by a contraction of the interior, as Dr. Davies has also 

 concluded. 



The clearest evidence was obtained from compound concretions in 

 the loess of Eastern Nebraska, of which illustrations are given. 

 Simple concretions abound there, and uniformly whenever they are 

 over an inch or two in diameter they are cracked inside. From them 

 there is little instruction on the point under discussion except that 

 the interior is of the same composition as the exterior, viz. fine silt 

 cemented with carbonate of lime. There is not more of clay in the 



' Bull. Geol. Soc. Am., vol. xiv, pp. 353 ff. 



