142 DESCRIPTION OF SPECIES. 



present epoch have a wide range of distribution; I he two species ( T. lati- 

 folia and T. angustifolia) are as common on the Norlli American continent 

 as they are in Europe. 



Hah. — Florissant; Randolpli County. U. S. Geol. Expl. Dr. Hayden. 



POTAMOGETON, Linn. 



Potamogeton? verticillatus, sp. nov. 



Plate XXIII, Figs. 5,6. 



Stems slender; leaves verticillate or tnfteil, grass-like, linear-lanceolate, largest 

 toward the base, sessile and narrowed to the point of attachment, nerved lengthwise 

 iu the middle; branches very slender, floating or pendant, bearing tufts of shorter 

 leaves. 



This species differs from its congeners by the position of the leaves 

 in verticils upon apparently articulate stems. It is distantly related to 

 F. coespitans, Sap., "Et.," i, p. 76, pi. iv, fig. 2. 



Hob. — Florissant. The specimen (fig. 5) is from the Explor. of Dr. 

 F. V. Hayden; the other belongs to the Princeton Museum. 



Potainogetoii yeiiiculatus, Al. Br. 



"Stizeiib. Verz.," p. 75; Heer, "Fl. Tert. Helv.," i, p. 102, pi. xlvii, figs. l-O; Ett., "Fl. v. Biliu," p. -.29, pi. vii, 

 figs. 1,2. 



Stems slender, branching, genicnlate-flexuous; leaves narrowly linear, acuminate, 

 fasciculate, sessile; fruits round or broadly oval-apiculato, 1 millimeter in diameter. 



Though the specimens merely represent the upper part of a stem the 

 characters of the leaves and the fructification refer the plant to Heer's 

 species. The fruits are slightly smaller, however, rather round than ovate 

 or exactly like those represented by the author, pi. xlvii, fig. be. 



Hah. — Florissant. No. 69 of Lacoe Collection. 



NAJADOPSIS, Heer. 



Najadopsis riig-ulosa, sp. nov. 



Plate XXIII, Fig. 7. 



Stem dichotomous from inflated apicial innovations; segments flat, dichotomous, 

 linear, acuminate, decurrent to the main stem; .surface merely irregular and minutely 

 wrinkled lengthwise, without trace of medial nerves. 



The substance of this plant is somewhat thick; the leaves or segments 



seem to have been originally cylindrical, though quite flat upon the stone, 



by compression? All that can be seen of the plant is figured. It has an 



