DEARTH OF SLATES AND BIKDSEYE ROCKS. 509 



We have observed slate only in division E, and here it occm'S in thin 

 hands or layers, rarely carrying Ostracoda of different species. 



Another point: Professor Emmons, in writing of the Birdseye formation,* 

 says : 



" The name, it is true, is not very appropriate, and besides there are other lime- 

 stones to which the term Birdseye has been given, but they are not likely to be con- 

 founded with the Birdseye of the Champlain group." 



But the mischief is that other rocks are thus confounded. A rock in B 

 of the Calciferous answers Professor Emmons lithological description of the 

 Birdseye, and Vanuxem j uses the very term in distinguishing a portion of 

 the Calciferous which is probably B, though he uses it to describe texture 

 and not to distinguish horizon. Again, the blue limestone of the upper part 

 of D of the Calciferous has the appearance and characteristic features of the 

 Birdseye, yet carries the abundant fauna of the Fort Cassin rocks. 



A third horizon, below the true Birdseye, is that occurring in C, the upper 

 division of the Chazy. Calymene multicosta, Hall, and Ulcenus crassicauda, 

 Dalmau, found at Isle la Motte, are assumed in the Paleontology of New 

 York, volume I, 1843, pp. 228-229, to be in the Birdseye. They belong, 

 however, to the dove-colored limestones of the upper Chazy, which elsewhere 

 underlie strata over 75 feet thick, composed largely of Rhynehonella plena. 

 Calymene is found at the same horizon elsewhere on the lake. Cyrtoceras 

 boycii, Whitf., Soa (!) lamottensis, Whitf, and Liehas ehamplainensis, Whitf., 

 belong also to the same bed of the upper Chazy. 



The Birdseye formation is very scantily represented in Vermont. Phytop- 

 sis tubulosum, Hall, has been seen only in the northwest corner of Benson, 

 and in a bed only about six feet thick. Elsewhere we find in this horizon 

 only a few feet of pure, fine-grained, brittle limestone, with fine lines of calc- 

 spar, without fossils, lighter in color than the known Black River strata just 

 above. 



Recapitulation and Suggestions. 



As indicated at the beginning of this discussion, our study of the Calcifer- 

 ous formation has brought us a series of surprises. The first was the thick- 

 ness of the rocks. It was only after repeated measurements that we were 

 willing to accept the fact that we were dealing with a series of rocks but 

 little less than 2,000 feet in thickness. This, too, at a horizon where the 

 very existence of a formation worth the name was a matter of question. 



The amount of maguesian limestone both surprised and perplexed us. 

 The masses of the various divisions are so alike that the attempt to place 

 them was at first discouraging ; but as we became familiar with the succession 



* Geology of N. Y., Report 2d District, 1842, p. 1">7. 

 t Geology of N. Y., Report 3d District, 1842, p. 30. 



LXVIII— Bill. Geol. Soc. Am., Vol. 1, 1880. 



