18S7.] 441 [Brinton. 



Beginning with the lowest stratum, tlie yellow sand, the only 

 clue offered to ascertain its age, believed by Dr. Flint to be 

 Eocene, is the shells which it offers in abundance, but apparently 

 only of one species. They are small and well preserved. Dr. 

 Flint transmitted a number of tliem for examination to Prof. 

 Newcombe, of Cornell TJniversit}' , who considered them a new 

 species, and has called them provisionally Pi/rula nicaraguensis, 

 and adds that the genus is represented in North America by but 

 one other species, P. nevadensis Stearn. 



I submitted a number of them to my collengue at the Academy 

 of Natural Sciences, Prof. Angelo Heilprin, wlio writes me : — 

 " I should not like to pronounce positively upon the age of the 

 deposit represented b}^ the Nicaraguan shells, as by themselves 

 they scarcely give direct evidence. But I should incline to the 

 opinion that the deposit in question is more nearly Post-pliocene 

 than Eocene, the specimens having a decidedlj^ new look, and 

 lacking the Eocene teitiar^^ characters." 



Dr. Flint sent to the Peabody Museum a number of leaves 

 from the deposit marked 1 4 on the section ; and I have recently 

 inquired of the authorities of the Museum whether their age 

 and character have been determined. They repl}', that these 

 characters have not yet been made out. 



The hard clay deposit, No. 7 of the plan, increases in thick- 

 ness in other localities to ten or twelve feet. It is considered by 

 Dr. Flint to represent a period of repose of many centuries, 

 and on its surface, bones of the mastodon have been found at 

 other points along the lake. It is the only deposit in the section 

 which seems to demand considerable time ; and even here, the 

 question will suggest itself whether a submergence of the lake 

 shore for a few centuries or less might not be sufficient to pro- 

 duce this deposit. The presence of the mastodon bones is no 

 evidence of great antiquity. That huge herbivore lived in 

 tropical America almost in historic times. A complete skeleton 

 of one was found not long since in an artificial salt pond, con- 

 structed by the Indians, near Concordia, Colombia. The pond, 

 with its bottom of paved stones together with the animal, had 

 been entombed by a sudden landslide.* 



* See R. B. White, "Notes on the Aboriginal I^aces of the Northwestern Provinces of 

 Soutli America," in the Jonrnnl of the Ant/iwpologiritl Institute of Great Britain, February, 

 1884, p. 244. 



PKOC. AMER. PHILOS. SOC. XXIV. 126. 3d. PRINTED DEC. 29, 1887. 



