Geology and Mineralogy. 245 



try unknown minerals, as my process gives me an easy method of 

 detecting any new substance or analyzing minerals however 

 many elements they may contain." 



II Geology and Mineralogy. 



1. Discovery of fish remains in Lower Silurian Hocks. — At 

 a meeting of the Biological Society of Washington, on February 

 7th, 1891, Mr. Chaeles D. Walcott, of the IT. S. Geological 

 Survey, announced the discovery of vertebrate life in the Lower 

 Silurian (Ordovician) strata. He stated that " The remains were 

 found in a sandstone resting on the pre-Paleozoic rocks of the 

 eastern front of the Rocky Mountains, near Canon City, Colorado. 

 They consist of an immense number of separate plates of placo- 

 ganoid fishes and many fragments of the calcified covering of the 

 notochord, of a form provisionally referred to the Elasmobranchii. 

 The accompanying invertebrate fauna has the facies of the 

 Trenton fauna of New York and the Mississippi valley. It ex- 

 tends upward into the superjacent limestone and, at an horizon 180 

 feet above the fish beds, seventeen out of the thirty-three species 

 that have been distinguished are identical with species occurring 

 in the Trenton limestone of Wisconsin and New York. 



" Great interest centers about this discovery from the fact that 

 we now have some of the ancestors of the great group of placo- 

 derm fishes which appear so suddenly at the close of the Upper 

 Silurian and in the lower portion of the Devonian groups. It 

 also carries the vertebrate fauna far back into the Silurian and 

 indicates that the differentiation between the invertebrate and 

 vertebrate types probably occurred in Cambrian time." 



Mr. Walcott is preparing a full description of the stratigraphic 

 section, mode of occurrence and character of the invertebrate and 

 vertebrate faunas for presentation at the meeting of the Geolog- 

 ical Society of America, in August, 1891. 



2. On Burrows and Tracks of Invertebrate Animals in 

 Palwozoic Rocks, and other Markings ; by Sir J. William 

 Dawson. (Quart. Jour. Geol. Soc, November, 1890, vol. xlvi. 

 (London) pp. 595-618). — The author states that in this paper it 

 is intended to contribute " Some recently acquired facts to the 

 solution of questions connected with these often problematical 

 markings." It is a well-known fact that the distinguished 

 author, who has contributed far more to the elucidation of the 

 American pre-Carboniferous flora than any other paleo-botanist, 

 has not claimed botanical affinities for many of the so-called 

 fossil plants ; but, on the contrary, has adduced proof of their 

 invertebrate or inorganic relationship. Dr. Dawson's investiga- 

 tions as a geologist and paleontologist, who has carefully studied 

 both invertebrate and plant remains of the Paleozoic rocks, gives 

 him a richer store of facts in reference to these organisms than it 

 had been the fortune of many other paleontologists to possess 

 who described and named many of the fossils under consideration. 



