200 RECOED OF SCIENCE FOR 1886. 



faults r.re odIj determinable in the trap shee's of tbe formation, and it 

 is found that the curvature of these and the overlap of their various 

 outcrops is caused by the slight and varying d.fferences between the 

 rango of the fault lines and the strike of the beds. 



The discovery of these faults indicate that the thickness of the forma- 

 tiou in the Connecticut Valley is very much less than formerly supposed, 

 for the repetition of beds produced by the upthrow of tbe dislocations 

 is always on the side of the direction of dip, allowing a moderate thick- 

 ness of strata to cover a broad surface area, and causing Irequeut out- 

 crops of the edges of the four or five trap sheets. 



34. The old notion that all the Triassic traps were intrusive is dying 

 out, largely owing to the work of Davis, who has found that in the Conn- 

 ecticut Valley the greater part of the trap has been poured out in broad 

 sheets as contemporaneous lava flows, and has pointed out the proba- 

 bility that the great masses forming the mountains in New Jersey are 

 of the same character ; a conclusion which is reached also by Iddings* 

 from a study of the columnar structure and microscopic character of 

 one of the sheets near Orange, New Jersey. 



The Holy ok 3 trap ranges of the Connecticut Valley have been con- 

 sid red overflows by Hitchcock and Davis, and this opinion is confirmed 

 by Emerson t from a very detailed study in Massachusetts, whore he 

 finds the trap to consist of two sheets. Rice | gives an account of the 

 relations found in the same ridge where it is crossed by tho Farmingtou 

 River, in Connecticut, and the two sheets and the surface features of the 

 lower flow are exposed. 



35. The question of the age of the Trias is as yet certainly known only 

 in a general way. Newberry considers the formation the equivalent of 

 Rhaetic beds of Germany from its flora, and states that while its fish 

 remains are mostly peculiar, they are more closely related to the Jura 

 and Cretaceous of the older world than to the Permian, and in the 

 Connecticut Valley represent groups confined to the foreign Jura. He 

 finds also that representatives of the Muschelkalk and Buuter are 

 wanting in the United States, and he considers the Ammonites, etc., 

 of Humboldt County, Nev., and the plants of Abiquiu, New Mex. 

 ico, and Los Broces, Sonora, to be Upper Triassic. He points out 

 that since no distinctly marked Jurassic fossils have been found east of 

 the Mississippi, and since the well-marked Jurassic of the Black Hills, 

 Utah, etc., overlies the Trias, tue use of the term Jura-Trias seems un- 

 warranted; and he supposes that the Permian proper of Europe, as 

 represented by the Zechstein and cui)riferous schists, has not been 

 found in America, and that there is here a break between the Upper 

 Carboniferous and the Trias.§ 



* Am. Jour. Sci., iii., vol. 31, pp. 321-331 and pi. 



t American Assoc. Proc, vol. 35, pp. 233-234. 



tAm. Jour., Sci., in. vol. 32, pp. 430-433. 



§ New York Acad. Sci. Trans., vol. 5, pp. 18-19; Am. Jour. Sci., in vol. 31, p. 154. 



