104 STUDIES IN GEOLOGY, No. i 



Corocoro. With the desire not to weight the exidence by 

 giving such considerations too great value, I prefer to let 

 Britton's identification stand. 



Genus Machaerium PERSOON 

 Machaerium eriocarpoides ENGEXHARDT 



Machaerium eriocarpoides Engelhardt, Sitz. Naturw. Gesell. Isis 

 in Dresden, 1894, Abh. i, p. 8, pi. i, fig. 28. 



Berry, Proc. U. S. Natl. Mus., vol. 54, p. 146, pi. 17, fig. 6, 1917 



Description. Leaflets petiolulate, lanceolate in outline, 

 nearly equilateral, with an equally pointed apex and base. 

 Margins entire. Texture subcoriaceous. Length, 1.2 to 

 1.4 cm. Maximum width, midway between the apex and 

 the base, 2.5 to 3.25 mm. Petiolule stout, 0.5 to i mm. 

 long. Midrib stout. Secondaries thin, regularly spaced, 

 subparallel ; six or seven pairs diverge from the midrib 

 at angles of about 45 and are camptodrome. Tertiaries 

 obsolete by immersion. 



This species is not uncommon at both Corocoro and 

 Potosi. While similar to several other fossil species 

 found at Corocoro and Potosi, it may be distinguished 

 from Acacia uninenn folia Engelhardt by its petiolule, 

 greater width and fewer secondaries ; from Enter olobium 

 grandi folium Engelhardt by its petiolule, its smaller size, 

 more prominent secondaries and more equilateral form ; 

 from Mimosites engelhardti Berry by its wider, less 

 elongated, and more lanceolate form, by its petiolule and 

 more prominent secondaries. According to Engelhardt it 

 is very similar to the existing Brazilian species Machcerium 

 eriocarpum Bentham. The last is recorded by Herzog 

 from the hill country of Velasco and from the broken 

 woods along the Rio Pirai and Rio Yapacani, in eastern 

 Bolivia. 



The existing species of Machanitm comprise over 60 

 trees or high climbing shrubs, with small pinnate leaves, 

 confined to the American Tropics, where they range from 

 the West Indies and Central America to southern Brazil. 



