168 



LARAMIE FLORA OF THE DENVER BASIN. 



Palaeoaster? similis Knowlton, n. sp. 



Plate XXIV, figures 10, 11. 



Palaeoaster? rimilis Knowlton [nomen nudum], U. S. Geol. 

 Survey Bull. 696, p. 427, 1919. 



Organism consisting of a whorl or rosette 

 apparently of about six thick, linear-lanceo- 

 late, acuminate, erect, one-nerved "leaves" 

 or segments which are sessile or nearly sessile 

 on a short, stout stem or axis. 



This form is represented by the nearly 

 perfect example figured and a number of de- 

 tached segments. So far as can be made out 

 this species consists of about six "leaves" or 

 segments which are disposed in a whorl at the 

 top of a short, stout branch or axis. The 

 individual "leaves" are narrowed to a long 

 wedge J shaped basal portion and apparently 

 are not in contact with one another. The 

 only nervation that can be observed is a 

 thick midrib. 



This species appears to be related to a curious 

 organism from the extreme upper part of the 

 Vermejo formation and the lowermost part of 

 the Raton formation of southern Colorado, 

 described under the name Palaeoaster in- 

 auirenda Knowlton, 09 as follows : 



It consists of usually about 9 (the number ranges from 8 

 to 12) narrow, erect "leaves" or members which are 3.5 

 to about 4.5 centimeters long and 6 to 10 millimeters wide' 

 in the middle. They are slightly narrowed to the sessile 

 base, where they are in contact, though evidently perfectly 

 free at the point of attachment. Above they are narrowed 



» Knowlton, F. H., TJ. S. Geol. Survey Prof. Paper 101, p. 278, pi. 

 49, figs. 5, 6, 1918. 



to a quite slender acuminate apex, which is usually some- 

 what incurved. The segments are thick and leathery, if 

 not indeed woody, and are traversed diversely by a deep 

 median furrow. * * * It seems probable that these 

 organisms were terminal, for there is some, evidence of the 

 presence of a scar or point of attachment at the base, but 

 there has never been noted any axis on which they might 

 have stood. They are certainly not leaves v whorled 

 around a stem, for had they been, some trace of the stem 

 should have been detected in some of the numerous speci- 

 mens that have passed in review. It appears more likely 

 that they were capsular in nature, for if the now spreading 

 segments were brought together they would apparently 

 make a tightly closed "capsule." The incurved tips of 

 the segments lend support to this view, though no evidence 

 of seeds or any interior structure has been observed. 



The specimen under consideration appears 

 to differ in several particulars from those above 

 described. Thus, instead of eight to twelve 

 "leaves" there are apparently only five or six; 

 instead of being in contact at their bases they 

 are slightly separated and have much more the 

 appearance of a whorl of leaves; and finally, 

 instead of being sessile they appear to stand 

 on a short stem or axis. The individual 

 "leaves" or segments are practically indistin- 

 guishable in the two forms, and the^ question 

 naturally arises whether they are slightly dif- 

 ferent phases of the same or similar organisms, 

 or whether they should be considered wholly 

 distinct. In the absence of sufficient material 

 it is deemed best to describe them as separate 

 species, and I have even questioned the generic 

 reference of the present form. 



Occurrence: Laramie formation, Murphy's 

 coal mine, Ralston County, west of Golden, 

 Colo. 



