AST. 23 THE ESMERALDA FORMATION BERRY 7 



Order NAIADALES 



Family NAIADACEAE 



Genus POTAMOGETON Linneaeus 



POTAMOGETON KNOWLTONI, new species 



Plate 1, figs. &-8 



I have referred to a single botanical species the abundant leaves 

 and fruits of an unusually well preserved Potamogeton^ a description 

 of which Doctor Knowlton was contemplating publishing at the time 

 of his death. This may appropriately be named in his honor and 

 may be described as follows : 



Floating leaves narrowly to broadly elliptical in outline, narrowly 

 to broadly rounded distad; the entire margins decurring proximad 

 to the broad flat petioles, which are sometimes preserved for lengths of 

 6 centimeters. These leaves range in size from 2.5 by 0.6 centimeters 

 to 5 by 2.25 centimeters, average sized specimens being shown in the 

 accompanying figures. The petioles, which are about 2 millimeters 

 wide, consist of a central, fairly stout vascular strand, bordered 

 throughout by the winged margins extending downward from the 

 leaf lamina and these show three or four thin parallel vascular 

 strands on each side. The mid vein of the lamina is about twice as 

 thick as the laterals. These are four to nine in number on each side, 

 diverging in the base and converging in the tip at about equally 

 acute angles. They are usually simple and aerodrome and approxi- 

 mately equally spaced, but occasionally one will fork a considerable 

 distance above the base. In the better preserved material each 

 alternate lateral is thinner than its adjacent fellows. All are 

 connected by thin obliquely transverse veinlets. 



The leaves are present in abundance in the clays and are strikingly 

 similar to the floating leaves of a number of still existing American 

 species such as Potaonogeton nuttalli Chamisso and Schlechtendal, 

 which, however, has shorter petioles, and Potamogeton faxoni 

 Morong. Species of Potamogeton are wide-ranging and variable 

 in their foliar characters, and no especial significance, either sys- 

 tematic or ecologic, can be attached to the above comparisons. 



The associated fruits, of which four or five specimens have been 

 detected among the leaves, are compressed as preserved in the clays, 

 about 3 millimeters in length and 2 millimeters in maximum diame^ 

 ter. The exocarp is rather delicate and frequently incompletely 

 preserved, with a smooth surface. The ventral margin appears to 

 have normally been nearly straight or slightly excavated, although 



