NO. 2151. FOSSIL PLANTS FROM FLORISSANT— KNOWLTON. 243 



United States National Museum collections. It is not described in 

 the present paper. 



A word may be said regarding the geological occurrence and strati- 

 graphic position of the fossiliferous lake beds at Florissant. So far 

 as now known the first geological account of the Florissant Lake 

 basin was made by Dr. A. C. Peale * who visited the area and made 

 a small collection of plants on October 11, 1873. In his account he 

 presented a map showing the approximate outhne of the ancient lake, 

 and in addition to the brief description of the beds and their abun- 

 dant fossil contents, gave a section of the succession of the strata as 

 observed in a low bluff just below the town of Florissant. 



In point of time apparently the next geological account of this 

 lake basin was given by Samuel H. Scudder,^ who visited the locality 

 in the summer of 1877. After quoting in full Doctor Peale's account 

 he presents his own observations which were made jointly with Prof. 

 Arthur Lakes. He gives descriptions of the beds, several geological 

 sections, and a revised map. It is probable that the Scudder collec- 

 tion of plants here reported on was made at this time. 



As the locaUty became more and more widely known for its fossil 

 resources, additional accounts were pubhshed, but it is not necessary 

 to review these in the present place. One of the latest and perhaps 

 best accounts is that given by Prof. Jmiius Henderson,^ based on the 

 results of a visit in 1905. 



From the several descriptions it appears that Lake Florissant was 

 a small lake approximately 5 miles in length and not much if any 

 exceeding a mile in width, but with a very irregular shore Hue. Hen- 

 derson says: 



The whole topography of the region indicates that the basin was formerly a mountain 

 valley and its laterals formed in granite by stream erosion. * * * The ramification 

 of the lake into lateral valleys and consequent tortuous outline gives a great length of 

 shore Une in proportion to the area. It consisted of two somewhat distinct bodies of 

 water connected by a narrow strait and placed at such an angle with each other as to 

 foi-m a wide L; or, to state it another way, the lake was nearly divided at the angle by 

 two promontories which jutted into it from opjwsite shores. 



That the lake was shallow is attested by the sun-cracking of some 

 of the shales, the character of the fish remains, and the erect stumps 

 of Sequoia. According to Henderson — 



The beds are comprised chiefly of volcanic ashes, mud, and sand, the component 

 particles of which are generally somewhat though not very much worn by the action 

 of water. The conclusion reached in both field and laboratoiy is that the deposits 

 were fonned largely by volcanic ashes from repeated eruptions falling upon the sur- 

 face of the water and settling to the bottom, assorted by the sluggish lake currents; 

 also by mud and ashes falling or flowing into position where they were rapidly washed 

 into the lake by rains, streams, and waves without much grinding. 



> Peale, A. C, U. S. Gaol, and Geogr. Surv. Terr., Ann. Rept. 1873 [1874], p. 210. 

 5 Scudder, S, H., U. S. Geol. and Geogr. Surv. Terr., Bull., vol. 6, 1882, pp. 279-300 

 8 Henderson, Junius, Univ. of Colorado Studies, vol. 3, 1906, pp. 145-151 



