94 STUDIES IN GEOLOGY, No. 4 



the actual living assemblage, but largely a result of the pre- 

 vailing coarseness of the sediments. Muds deposited in quiet 

 coastal waters like the lagoons along the lower Eocene coast 

 of the Mississippi embayment are the materials in which 

 great quantities and varieties of leguminous leaflets are pre- 

 served. An apt illustration of the influence of the matrix 

 is obtained by comparing the synchronous fossiliferous beds 

 at Corocoro and Potosi in Bolivia. The former are coarse 

 and contain few recognizable species, the latter are fine 

 grained and contain an astonishing variety of mostly small 

 leguminous leaflets. 



The family Caesalpiniacese is represented in the fossil flora 

 of Chile by the abundant pods of one species and the leaflets 

 of two species of the large genus Cassia. The Papilionacese 

 comprise species of Copaifera, Desmodium and two that 

 are referred to the form-genus Leguminosites but are sug- 

 gestive of Erythrina and Copaifera. The latter genus with 

 about a score of existing species is mostly American but is 

 sparingly represented in the African tropics. The nearest 

 existing species to Chile are in the lower montana country of 

 Bolivia, but the genus is represented in the Pliocene deposits 

 of that country at both Corocoro and Potosi. 



The order Geraniales is rather well represented by the 

 families Erthroxylaceae, Rutacese, Meliacese, Vochysiaceae and 

 Euphorbiaceae. The first by a single species of Erythroxylon 

 from Curanilahue. The material is fragmentary but the 

 venation appears to represent this genus, which has nearly 

 one hundred existing species largely confined to the American 

 tropics, but represented from tropical Africa through Asia 

 to northern Australia. The fossil species closely simulates 

 an existing Brazilian one. 



The Rutaceae is one of the large families in this flora with 

 representatives of the four genera Zanthoxylon, Tkorea, Pil- 

 ocarpus and Erythrochiton. The first with two species, which 

 have been compared with the existing Z. sprucei Engler of 

 eastern Peru and Brazil, and Z. aromaticum of Colombia 



