FLORA OF THE DAKOTA GROUP. 57 



horny; the great divergence of the lateral lobes nearly at right angles 

 to the medial nerve and also generally curved down; the middle lobe is 

 ahvays comparatively short and broad. 



Sassafras (Araliopsis) dissectuni, sp. nov. 



Leaves very large, long and narrowly cuneate to the petiole, palmately five-lobate 

 by subdivision of the lateral lobes diverging at an acute angle from the medial one. 



The leaves of this form are very large, some measuring 22 centimeters 

 from the top of the petiole to the apex, 20 centimeters between the extrem- 

 ities of the lateral lobes. The base is narrowly cuneate, long, decurring 

 to the petiole; the three primary divisions are joined in obtuse but narrow 

 sinuses; the lateral ones at an acute angle of divergence are cut into two 

 short obtuse dentate lobes, while the middle one is taper-pointed, not 

 lobed, but deeply undulate-dentate. This form might be considered as a 

 var. of S. mirahile, but if differs greatly in the general facies, the lateral 

 lobes oblique erect lobed and unequilateral, the lateral primary nerves 

 alternating at base or joined to the medial at a distance from each other, 

 the long lanceolate undulate-dentate middle lobe and in the nervation, 

 the primary nerves being thick indeed, while the secondary nerves and 

 their branches are thin, generally effaced along the borders. 



Hah. — This form has not been seen among the numerous specimens 

 of fossil plants examined from the Dakota C4roup until recently. It is 

 represented in the collection of the Museum of Comp. Zool. of Cambridge 

 by a number of fine specimens, all obtained from 3 and 7 miles north of 

 Fort Harker by Clis. Sternberg. 



Sassafras (Araliopsis) recurvatum, Lesqx. 



Platanus recurvata, Lesqx., " U. S. Geol. Rep.," vi, p. 71, pi. x, figs. 3-5. 



Leaves three to five palmately lobed ; lobes nearly equal in length, the medial 

 broader; lateral nerves curving downward, either simple with mere secondary veins or 

 forking above the base; lobes undulate or obtusely dentate on the borders. 



This form is evidently transient in its characters. By the cuneate 

 and decurrent base of the leaves joining the petiole at a distance below 

 the point of union of the three primary veins and by the trilobate division, 

 it is a Sassafras. But by the irregularity of the lobes or the subdivisions 

 of the leaves in lobes and teeth, it seems referable to Platanus, while a 

 tendency to become five-lobate by the forking of the lateral nerves is a 



