2 STUDIES IN GEOLOGY, No. 3 



made by Mr. E. P. Larkin and Professor F. H. Bradley. 

 The fossils, which were collected in 1867, were labelled "Zor- 

 ritos, Peru," and comparisons made during the present 

 study indicate that most of them were probably from the 

 three members of the Zorritos formation. Nelson men- 

 tioned 36 species of gastropods and 24 of pelecypods ; of 

 the gastropods he named 19 species, and of the pelecypods 

 8 species, mentioning the remainder as indeterminate. 



Nelson's work carries very little biologic and no geologic 

 significance. His comparisons were made with recent forms 

 only, and as a consequence of his omission of reference to 

 fossil species his work serves, as he states, (p. 186) simply as 

 "a catalogue of the genera found in the collection, with 

 descriptions of part of the species." Although most of his 

 descriptions are good, the small number of figured speci- 

 mens made his work difficult to deal with until his collection 

 was loaned by the Peabody Museum. 



Between 1870 and 1899 nothing was published on the 

 geology and paleontology of the area. In the latter year 

 Josef Grzybowski, 3 then an assistant in the Geological Insti- 

 tute of Cracow, published the first account of the geology of 

 the region. With his geologic data Grzybowski included a 

 study of mollusks collected by him, of which he described 

 35 species from the Zorritos formation, 14 of gastropods 

 and 21 of pelecypods. It should be noted that the fossil- 

 iferous beds designated by Grzybowski as Heath have been 

 proven to be Zorritos in age ; the fossils "catalogued by Grzy- 

 bowski as Heath are thus Zorritos. Fuller treatment of 

 that matter will be offered in the discussion of the stratig- 

 raphy. The interesting fact that of Grzybowski's 35 species 

 only two were recognized by him as identical with species 

 described by Nelson, and that the present work, with the 

 advantage of Nelson's collection, shows only 6 species to be 



3 Die Tertiarablagerungen des nordlichen Peru und ihre Mol- 

 luskenfauna, Neues Jahrb., Beil. Bd. 12, pp. 610-664, pis. 15-20, 1899. 



