GENERAL EEMARKS. 201 



fossils of this last locality have a peculiar interest, from the occurrence of 

 Leiorhynclms quadricostatus, Hall, a form which characterizes the black slates 

 (Genesee Slates) at the top of the Hamilton group of New York, and also a 

 species of LunuUcardium {L, fragosa =: Posidonomya fragosa Meek). The 

 occurrence of these two species, together with an Aviculopeden, scarcely dis- 

 tinguishable from A. equilatera (-^Avicula equilatera H., Geol. Rept., 4th 

 Dist. N. Y., p. 18Q, fig. 7), would appear to be sufficient reason for consid- 

 ering these shales of an earlier date than the Carboniferous, and much more 

 nearly related to the Devonian Black Slates of New York. It is true there 

 are black slaty layers, bearing Carboniferous fossils, immediately above 

 them, or separated from them by only a thin bed of sandy calcareous shales, 

 as at Eberhardt Mill; but these upper layers are lithologically quite dis- 

 tinct from those below, being, in fact, a bituminous limestone; and the 

 fossils are so entirely distinct and strongly Carboniferous in character, 

 one of them {CardiomorpJia Missouriensis S.) being positively identical with 

 a well-known Coal-Measure species, that it appears to us there can be no 

 doubt of their Carboniferous age and entire distinction from those below. 

 The specimen of sandy calcareous shale in the collection, marked as occur- 

 ring in the black slates at Eberhardt Mill, contains fragments and imperfect 

 individuals of a Spirifer, resembling S. Keokuk H., but too imperfect for 

 positive identification. If this specimen is authentic in its location, it 

 undoubtedly marks a line of separation between the two beds of black 

 slates. 



Another group of fossils of considerable interest will be found figured 

 on plate IV. These were obtained from limestones at Dry Caiion, Oquirrh 

 Mountains ; and from Ogden, Little Cottonwood, and Logan Canons, in 

 the Wahsatch Range, Utah, from their character we should consider them as 

 of about the age of the Waverly group of Ohio and the yellow sandstones 

 of Burlington, Iowa; which have been referred to the same age. Some 

 of the species are identical with forms described from these localities, 

 while others are very closely representative species; and all have more 

 of a Devonian than a Carboniferous aspect. The occurrence of so many 

 Devonian types at several localities within a limited district, and in 

 considerable numbers, showing that it is not an accidental feature of an 



