54 



CONTRIBUTIONS TO PAL^ONTOLOGY 



Ficus pseudopopulxis Lesquereux (in part), Knowlton, U. S. Geol. Surv. Prof. Paper 101, 304, pl. 72, figs. 3, 4 



only, 1917; idem, Prof. Paper 134, 83, pl. 7, fig. 4, pl. 9, fig. 3, 1924; idem, Prof. Paper 155, 66, only pl. 25, 



figs. 3-5, 1930. 

 Ficus neoplanicostata Ivnowlton (in part), U. S. Geol. Surv. Prof. Paper 101, 303, pl. 73, fig. 4, pl. 74, figs. 2, 3, 



pl. 76, fig. 4, 1917; idem, Prof. Paper 134, 82, pl. 9, fig. 4, 1924; idem, Prof. Paper 155, 69, only pl. 28, 



figs. 3-7, 1930. 

 Ficus prcelatifolia Ivnowlton, U. S. Geol. Surv. Prof. Paper 98, 338, pl. 87, fig. 4, 1917. 

 Pterospermites neomexicanus Knowlton, ibid., 341, pl. 90, fig. 6. 

 Ficus impressa Knowlton, U. S. Geol. Surv. Prof. Paper 130, 134, pl. 7, figs. 1-3, pl. 16, fig. 3, 1922. 



The specimens from Black Buttes, Wyoming were originally described by Lesquereux as 

 f ollows : 



"Leaves of medium size, subcoriaceous, entire, elliptical or broadly oval, .slightly acuminate 

 or obtuse, rounded to a short, thick, petiole, palmately three-nerved from the top of tbe petiole, 

 rarely from a short distance above the base; primary and secondary nerves broad, fiat, all campto- 

 drome, as well as their divisions." 



Leaves of precisely this description are by f ar the most abundant of all species in the Medicine 

 Bow collections. Over 50 specimens of complete or nearly complete leaves were collected for 

 study. In arranging this suite for identification it was apparent that there was a perfect series 

 from small ones 1.2 by 2 cm. in dimensions to very large ones 7 by 12 cm. It was also found possi- 

 ble to match individual specimens perfectly with the figures and type specimens of each of the 

 species listed in the above synonymy. These various species had been distinguished from Ficus 

 planicostata by minor details, chiefly of venation, but were in each case discussed as difficult to 

 separate from that species. They are here regarded as mere variants of the average leaf form. 



In 1923 Berry discussed the difficulties involved in the taxonomic separation of leaves of this 

 type and concluded that Ficus planicostata and its varieties were be.st considered conspecific with 

 Ficus mississippiensis (Lesquereux) Berry.' In comparisons of my large suite with all available 

 specimens of both these species and others at the U. S. National Museum I have found, however, 

 that the following criteria can serve to distinguish them: 



Ficus planicostata 



1. Size: 



Average less than 10 cm. long. 



2. Shape: 



Always elliptical or broadly oval, widest near the 

 middle. 



3. Tip: 



Always obtuse and abruptly narrowed to a blunt 

 point. 



4. Venation: 



Lateral primaries basilar. 



Ficus mississippiensis 



1. Size: 



Average more than 10 cm. long. 



2. Shape: 



Always ovate or ovate-lanceolate, widest well 

 below the niiddle. 



3. Tip; 



Always acute and graduaUy narrowed from the 

 middle of the leaf to a long, slender point. 



4. Venation: 



Lateral primaries suprabasilar. 



It must be admitted, of course, that it is largely a matter of taxonomic judgment as to which 

 characters of leaves are more or less important in distinguishing one species from another. In this 

 case, however, I feel that my conclusions were inevitable because of the constancy with which the 

 listed characters were maintained in so large a collection of leaves of all sizes. 



As here conceived, Ficus planicostata is a valuable index of late Cretaceous deposits in the 

 Rocky Mountain region, though it may possibly range into the early Paleocene. It makes its 

 first appearance in the upper Mesaverde formation of Wyoming, is well represented in the Vermejo, 

 Raton, Fruitland, and Animas formations, and is abundant in the Laramie, Denver, and Black 

 Buttes floras. Although it has been reported from only one locality in the Lance,^ I have seen 

 other specimens of it from the Lance of "Conver.se County," Wyoming, at the U. S. National 

 Museum, which Knowlton referred to Phyllites ficifolia, new species.' The species has never been 

 found in beds of indisputable Paleocene age, although collections from such beds, namely the Fort 

 Union formation, are very extensive. Related descendants of this species, such as Ficus inississip- 



' Berry, E. W., U. S. Geol. Surv. Prof. Paper 131-A, 9, pls. 6-8, 1923. 

 «Knowlton, F. H., Washington Acad. Sci. Proc, vol. 11, 211, 1909. 

 ' Knowlton, F. H., unpublished manuscript. 



