SCIENTIFIC EXPEDITION TO NORTHWESTERN COLORADO 1 49 



being a sandstone and the leaves poorly preserved, while the higher one 

 is a fine clay and the fossils are in good condition. 



The Ostrea-Micronema horizon south of Axial appears to occur nearer 

 the middle of the Mesa Verde formation than any of the other faunas 

 or floras, though it was impossible to be sure of this without more time 

 for the examination of the region. The specimen of Geinitzia reichen- 

 bachi stem discussed by Professor Cockerell was found at this point 

 lying on the surface but apparently having come from a few feet below 

 the Ostrea and Micronema. The two latter fossils form here a ledge of 

 black limestone two or three feet in thickness composed almost entirely 

 of shells. Several such ledges composed of Ostrea and Corbicula occur 

 north of Blythe's house, and the Corbicula-Micronema ledge at Rifle Gap 

 is a solid mass of shells 



Fossil Plants from the Mesa Verde Cretaceous 



By T. D. A. Cockerell 



The flora of the Mesa Verde formation appears to be practically 

 identical with that of the Laramie. Lists of species have been given by 

 Knowlton in Bulletins 350 and 371 of the U. S. Geological Survey. Ficus 

 is prominent, with several species, separable from each other thus : 



Apex of leaf somewhat produced; a rounded lateral lobule. . . . squarrosa Knowlton. 

 (This is a species of the Montana formation; the identity of the Mesa Verde 

 plant is considered doubtful.) 

 Apex of leaf not produced, at most very broad-angled. 



Base deeply cordate; size very large .... speciosissima Ward. (Also a 



Montana formation species.) 

 Base not at all cordate. 



Leaf longer than broad .... planicostata Lx. 

 Leaf broader than long .... latijolia (Lx.) Kn. 

 (Both these are characteristic Laramie species.) 



There are also Araucarian conifers, palms, cinnamon, magnolia, 

 and various other trees, all indicating a moist and warm climate. Frag- 

 ments of a dinosaur have been found, and eight genera of aquatic 

 mollusca. 



