208 UNITED STATES GEOLOGICAL SUHVEY— TERTIARY FLORA. 



varying in size fiotn one tu four centitnefers hmad nnd one to two and a liaH 

 centimeters long only, merely represent a local variety, var. minor, while 

 those of Golden may belong to the normal form. The species appears to be 

 rare in the Tertiary of Europe, where it has been seen until now only in the 

 plastic clay-beds of Bilin. 



Habitat. — Golden, Colorado, in fragments of large leaves; Point of 

 Rocks, Wyoming, mixed with the floating plants, wiiicli are represented ujion 

 the same plate (Ixi, figs. 1 to 17) {Dr. F. V. Haydcn, Wm. Cleburn). 



OLERACE^. 



POLYGON EyE. 



COCCOLOBA, Jacq. 



The leaves of this genus are generally broadly oval, coriaceous, rounded 

 to a short petiole, all penninerved, with the divisions of the lateral veins 

 irregular. The present species inhabit the tropical and subtropical regions, 

 mostly of the American continent; some of them are found in Cuba, and .two 

 at least as far north as Florida. Two species only have been described as fossil, 

 both in the Foss. Fl. of Bilin, by d'Eltingshausen, from the Middle Miocene. 



Corcoioba laevigata. Lesqx. 

 Plate XXXV, Fig. 7. 

 Coccoloba lon-tgata, Lesqx., Annual Report, 1872, p. 3d7. 



Leaves membranaceons or subcoriaceous, very entire, round, rather broader than long, apparently 

 very obtuse, abruptly oontracted at the base, and slightly decurring lo the inflated midrib; surface 

 smooth. 



Two fragments only, and both alike, have been found of these leaves, 

 which are nearly round, or broader than long, of a comparatively small size, 

 four and a half centimeters across, with borders apparently reflexed, very 

 entire, merely undulate. The midrib is enlarged and flattened from below 

 the middle of the leaves downward; the lower lateral veins closer, irregular 

 in distance and direction, on an open angle of divergence ; the upper ones 

 more oblique, or branching underneath, and anastomosing in double or triple 

 bows to the borders. The nervation is irregular, like that of the leaves of some 

 species of this genus, C.Jloridana, Meiss., for example, or one of its varieties, 

 which was found in cultivation at Key West. Its leaves are smaller, some of 

 them either gradually narrowed or abruptly contracted at the base, as in the 

 fossil species, with the marginal veinlets either following the borders and nor- 

 mally anastomosing with branches of the secondary veins, or passing straight 



