PREFACE. V 



Doctor MacDonald's reports to the Canal Commission have been 

 published in the annual reports of the chairman of the Canal Com- 

 mission; and he is the author of a more lengthy paper entitled 

 ''Some engineering problems of the Canal Zone in their relation 

 to geology and topography," published as Bulletin 86 of the United 

 States Bureau of Mines. x Since the termination of his services for 

 the Canal Commission he has completed a large report on the 

 physiography, stratigraphic and structural geology, petrography, 

 and economic geology of the Canal Zone. The transmission of this 

 memoir for publication has been delayed because some of the paleon- 

 tologic determinations were needed for interpreting the geologic 

 history. 



After the agreement to the proposed plan of cooperation, I took 

 charge for the United States Geological Survey of the preparation 

 of the special paleontologic reports, of the problems of geologic 

 correlation, and of the coordination of the investigations with other 

 work on the physiography, stratigraphy, paleontology, and geologic 

 history in the southeastern United States and the West Indies. The 

 paleontologic material was sorted according to groups, and the 

 following specialists undertook monographic reports: 



Dr. Marshall A. Howe, calcareous algae. 



Prof. Edward W. Berry, higher plants. 



Dr. Joseph A. Cushman, foraminifera. 



Dr. T. Wayland Vaughan, madreporarian corals. 



Dr. Robert T. Jackson, echinoids. 



Dr. C. Wythe Cooke, mollusca. 



Mr. F. Canu and Dr. R. S. Bassler, bryozoa. 



Dr. Mary J. Rathbun, decapod Crustacea. 



Prof. H. A. Pilsbry, cirrepedia. 

 The few vertebrates obtained were identified by Mr. J. W. Gidley. 

 All of the paleontologic reports are now complete except that on the 

 mollusks. It was at first hoped that Dr. W. H. Dall would prepare 

 the one on this group, but pressure of other work prevented him. 

 Later Dr. C. Wythe Cooke, paleontologist of the United States 

 Geological Survey, began a study of the collection of mollusks, but 

 other duties have interfered with his prosecution of it. The recent 

 papers by Toula 2 and by Brown and Pilsbry 3 have been used, and 

 they are valuable, but they do not meet the needs of the present in- 

 vestigation, for the material described in them mostly represents 

 one geologic formation, the Gatun formation, and the stratigraphic 



i U. S. Bureau Mines Bull. 86, pp. 88, 29 pis., 9 text figs., 1915. 



2 Toula, Franz, Eine jungtertiiire Fauna von Gatun am Panama- Kanal, Geolog. Reichsanstalt Wien 

 Jahrb., vol. 58, pp. 673-760, pis. 25-28,15 text figs., 1909; Die jungtertiare Fauna von Gatun am Panama- 

 Kanal, Ibid., vol. 61, pp. 487-530, pis. 30,31,1911. 



« Brown, Amos P., and Pilsbry, Henry A., Fauna of the Gatun formation, Isthmus of Panama, Acad. 

 Nat. Sci. Phila. Proci for 1911, pp. 336-373, pis. 22-29, 3 text figs., 1911; Fauna of the Gatun formation, 

 Isthmus of Panama, II, Acad. Nat. Sci. Phila. Proc.for 1912, pp. 500-519, pis. 22-26, 5 texts figs., 1913. 



