108 ANNALS NEW YORK ACADEMY OF SCIENCES 



is shown that the so-called Ogden quartzite is an overthrust block of 

 partly Algonkian and Cambrian quartzite and shale, lying upon limestone 

 of Devonian age. Blackwelder has recently shown that the same relation 

 exists in Ogden Canyon and that the Ogden quartzite does not exist as 

 originally defined. It now appears that the typical Ute limestone also has 

 no existence as a regular depositional unit but is in reality the lower part 

 of what was called the Wasatch limestone. The name Ute limestone, 

 therefore, must go the way of the Ogden quartzite and be discarded. The 

 Fortieth Parallel section is thus reduced over 3000 feet in thickness by 

 the elimination of these two members. No name has yet come into gen- 

 eral use for the Silurian strata of the northern Wasatch as they have been 

 little studied, but the one employed by Blackwelder, viz., Paradise lime- 

 stone, might serve. In the central Wasatch, this is apparently wanting 

 altogether. 



The absence of Silurian strata in the central Wasatch may be due to 

 non-deposition or to their complete removal by erosion. The only evi- 

 dence of a great erosion interval in this part of the section is that already 

 mentioned at the top of the Maxtield formation. Limestone conglom- 

 erates, however, are looked upon with suspicion as forming true basal 

 beds since the discovery of the intra-formational types. Nevertheless, 

 there is no reason why this could not be a basal conglomerate upon an old 

 erosion surface, for limestones of Lower Ordovician age are of wide dis- 

 tribution in the west. 



DEVONIAN STRATA 



Below the lowest Productus horizon of the Mississippian in the Cotton- 

 wood region occurs a cherty limestone in w^hich there are abundant corals 

 of a few species. Fossils apparently from this horizon were reported by 

 Professor Sanborn Tenny^^ of Williams College as early as 1873. He 

 described the locality as follows : 



"In a position southeast? of Great Salt Lake City on the divide between 

 Great Cottonwood and Little Cottonwood, 9,000 feet to 10,000 feet above sea, is 

 a dark blue limestone, containing corals." 



The corals collected were two species of Zaphrentis and one of Syringo- 

 pora, which E. P. Whitfield called Syringopora maclurei Billings but re- 

 garded as probably a new species. These were roughly referred to the 

 Upper Helderberg horizon. 



Little attention, apparently, has been given to the paper by Professor 



1* S. Tenny : "Devonian Fossils from the Wasatch Mountains, Utah," Am. .Totir. Set. 

 3rd Ser., Vol. 5. 1873. 



