Berry — An Eocene Ancestor of the Zapodilla. 213 



these large-fruited genera have been derived from the small- 

 fruited genera, and in the present state of our knowledge 

 Eoachras is the earliest of the large fruited forms. 



Regarding the existing distribution of Achras and Calo- 

 carpum, this is masked by prehistoric cultivation. Both 

 genera are endemic in the American tropics. Achras is 

 indigenous in Mexico south of the Isthmus of Tehuantepec, in 

 Guatemala, Salvador and northern Honduras. Pittier says 

 that it is especially abundant in the lowlands of Tabasco and 

 Chiapas and in western Yucatan. Throughout the balance of 

 Central America and the West Indies it has not been definitely 

 decided whether it is endemic or not. It appears to be also 

 native in Colombia and Venezuela. The two existing species 

 of Calocarpum are natives of Central America, and possibly 

 the West Indies and the northern part of South America. 



Johns Hopkins University, Baltimore. 



Explanation of Plate I. 



Fig. 1. — Eoachras eocenica gen. et sp. nov. — lateral view, natural 

 size, from the Middle Eocene (Claiborne Group) of Mississippi. 

 Fig. 2. — The same, distal view. 

 Fig. 3. — The same showing the umbilical area. 

 Figs. 4, 5. — Achras zapota Linne (after Pittier). 

 Figs. 6, ?. — Calocarpum viricle Pittier (after Pittier). 

 Figs. 8, 9. — Calocarpum mammosum (Linne) Pierre (after Pittier). 

 Fig. 10. —Lucuma salicifolia H. B. K. (after Pittier). 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Molecular Weight of Sodium Carbonate and the 

 Atomic Weight of Carbon Referred to Silver and Bromine. — 

 Richards and Hoover introduce their account of this research 

 by the remarks, that the investigations concerning radio-activity 

 have increased rather than diminished the interest in atomic 

 weights ; that the recent indications that the atomic weight of 

 lead may be variable stimulates further research ; that whether or 

 not the atomic weights may vary in a few cases they still remain 

 the most fundamental figures that are known to science ; and that 

 no amount of trouble is too great to secure a satisfactory knowl- 

 edge of these numbers. 



Using the greatest care and skill, the account of which is fas- 

 cinating reading, these investigators have started with pure sodium 



