218 STUDIES IN GEOLOGY, No. 4 



This species is quite similar to Ccesalpinia gmehlingi 

 Engelhardt from Potosi, Bolivia, 9 but is more inequilateral 

 and more coriaceous. The two are probably closely related. 

 It is also much like the existing Casalpinia fioribunda Tul. of 

 the Amazon basin. 



The genus is abundantly represented in the fossil record 

 from the Upper Cretaceous onward, and the two score or 

 more recent species are found in the tropics of both hemi- 

 spheres, and are especially well represented in the Amazon 

 basin and in the valleys of the eastern Andean slopes. 



Order MYRTALES 



Family MELASTOMATACE^ 



Genus MEXASTOMITES Unger 



Melastomites sp. 



PLATE I Fig. 8 



Fragments of a lanceolate leaf about 3 to 3.5 centimeters in 

 length and I centimeter in maximum width almost certainly 

 represent a fossil species of this family. The texture is sub- 

 coriaceous, and there are 5 relatively stout, aerodrome pri- 

 maries connected by thin transverse nervilles. 



The presence of a member of this family at Jancocata 

 throws an interesting light on the physical conditions at the 

 time the fossil species lived. The Melastomataceae is a large, 

 prevailingly American family, of distinctly humid climate 

 types and almost strictly tropical in its distribution. There 

 are between 2,000 and 2,500 species in the existing flora of 

 the western hemisphere, chiefly in the Antilles, Central and 

 tropical South America, especially in the Amazon basin. 

 In Bolivia species occur abundantly in the montafia country, 

 but do not, as far as I know, occur west of the divide of the 

 Eastern Andes. Nothing similar has thus far been discov- 

 ered in the Pliocene floras of Potosi or Corocoro. 



9 Berry, E. W., U. S. Natl. Museum Proc., vol. 54, p. 141, pi. 16, 

 fig. 14, 1917. 



