NO. 2229. FOSSIL PLANTS FK021 BOLIVIA— BERRY. 131 



Martius, and Inga halnchetiana Bentham, and is closest to the last, 

 a Brazilian species. 



The genus Inga contains a considerable number of fossil species 

 and is found as early as the Upper Cretaceous in North America. 

 There are several well-marked forms in the lower Eocene of the Mi-s 

 sissippi embayment region. Tiie existing species, upward of 200 

 in number, are confined to the American Tropics and reach their 

 maximum of abundance and variation in the Brazihan region where 

 about (i6 species are already known. Tropical Peru ranks next in 

 number of species with about 30. All of the five sections of the 

 genus are represented in the existing flora of Bolivia with a total of 

 12 known species, all of which, so far as I know, being confined to 

 eastern Bolivia. 



Genus PITHECOLOBIUM Martius. 



PITHECOLOBIUM BRITTONIANUM, new species. 



Plate 15, fig. 20. 



Cassia chrysocarpoides Britton, Trans. Amer. Inst. Min. Eng., 1893, fig. 36 (not 

 figs. 29-35, 37). 



Description. — Leaflets sessile, inequilateral, elliptical in general 

 outline, with an emarginate tip and an inequilateral base which is 

 straight on one side and full and rounded on the other. Length 

 about 1.6 cm. Maximum width, about midway between the apex 

 and the base, about 11.5 mm. Margins entire, full. Texture cori- 

 aceous. Midrib stout, curved, prominent on the low^er surface of the 

 leaflet. Secondaries numerous, subparrallel, comptodrome. Ter- 

 tiaries obsolete. 



This species is based on leaflets collected by Wendt and ques- 

 tionably referred by Britton to Cassia chrysocarpoides of Engelhardt^ 

 to which they are not related. It is the second species of Pitlieco- 

 lohium to be recorded from Potosi and is based upon more complete 

 material than Pithecolohium tertiarium Engelhardt.^ The fossil forms 

 that have been referred to this genus are few in number, and include, 

 in addition to the species already cited, two well-marked species from 

 the lower Eocene and one from the lower Oligocene of the Mississippi 

 embayment and a fourth species from the Tertiary of Colombia. The 

 present Potosi species is very similar to Pithecolohium oligocaenum 

 Berry ^ from the lower Oligocene of Louisiana. 



The genus comprises considerably over 100 existing species, many 

 of which are large trees and found in all tropical countries. Three- 

 fourths of the species are confined to America, where they range from 

 the West Indies and Central America to southern Brazil. Among 



lEngelhardt, H., Sitz. Naturf. Gesell. Isis in Dresden, 1887, Abh, 4, p. 37, fig. 15. 



» Idem., 1894, Abh. 1, p. 12. 



3 Berry, E. W., U. S. Geo). Survey Prof. Paper 98M, 1916 p. 239, pi. 55, fig. 10 



