GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


calcareous sandstone in the measured section at canal station 1759. MacDonald (1919, p. 537) assigned to the Emperador "somewhat sandy limestone" at locality 99g (canal station 1606). The matrix of the numerous fossils MacDonald collected at that locality consists of sandy limestone that does not resemble the Emperador limestone.
 FOSSILS AND AGE
 Smaller Foraminifera.-A few species of smaller Foraminifera from the Culebra formation were recorded by Cushman (1918). Some of the localities referred to the Culebra in Cushman's publication represent other formations: Geological Survey localities 6009 and 6010 represent the La Boca marine member of the Panama formation; localities 6024a, 6025, and 6026 the Caimito formation. Though the fauna of the Culebra is not extensive, more species than the few recorded by Cushman are represented in core collections obtained during the operations of the Geological Section of the Special Engineering Division. Meager collections can still be obtained at outcrop localities, such as localities 104 and 108. It has been claimed that Siphogenerina transversa is not found in the Culebra formation (Woodring and Thompson, 1949, p. 241). M. N. Bramlette, however, identified a small specimen of that species in core material from a depth of 88 feet (26.7 meters) in core hole SL108 and another small specimen from a depth of 133 feet (40.4 meters) in the same core hole. Core hole SL108 was located 1.1 kilometers westsouthwest of locality 101 and evidently the Culebra formation was penetrated at the depths just specified.
 Larger Foraminifera.-Cushman's identifications of the species of Lepidocyclina in the Culebra formation have not been confirmed (Cushman, 1918a,p.90). H.G. Schenck identified Lepidocyclina canellei in core samples at horizons 30 to 45 meters below the top of the Culebra (Woodring and Thompson, 1949, p. 238). Cole recently described and illustrated L. miraflorensis (locality 99g) and L. waylandvaughani (locality 99a) from the Culebra formation proper, and L. miraflorensis (locality 119a) from the Emperador limestone member (Cole, 1953a). The type localities of Miogypsina cushmani (locality 107) and "Orbitolites" americana


(locality 100) are in zthelCulebra formation. Mioj gypsina intermedia is recorded from the Culebra at locality 115 near Paraiso (Drooger, 1952, p. 36).
 Corals.-Of the four species of corals recorded by Vaughan from the Culebra formation proper, one occurs' in the Emperador limestone member, three in the Antigua formation, and all in the Anguilla formation (Vaughan, 1919a, p. 208; Geological Survey locality 6026 represents the Caimito formation). Vaughair listed 24 species of corals from the Emperador limestone member. Four of them occur in the Antigua formation and nine in the Anguilla formation (Vaughan, 1919a, p. 209; Geological Survey locality 6024b represents the Caimito formation and 6256 the La Boca marine member of the Panami formation).
 Molluskls.-MacDonald made numerous collections of mollusks from the Culebra formation during the excavation of Gaillard Cut. Much of the material, however, is poorly preserved. Except in the Paraiso area, the Culebra fauna includes species indicating brackish water, particularly in the transition zone between the Culebra and Cucaracha formations (localities 110 to 112a). The Neritina, for example, indicates brackish water and Littorina angulifera is a modern species that lives in mangrove swamps. Most of thespecies indicating brackish water are absent in the Paraiso area (localities 113 to 116). Plate 2 indicates that the fossiliferous strata in the Paraiso area are, close to the top of the Culebra. It has been suggested that the uppermost part of the formation in the Paraiso area is the equivalent of the transition zone but represents an environment farther seaward (Woodring and Thompson, 1949, p. 239). According to the evolutionary scheme worked out by Drooger for miogypsinids, however, Miogypsina intermedia, which occurs in the Paraiso area, is less advanced than M. cushmani, found in the upper part of the Culebra farther northwest (locality 107), where the transition zone is not known to be present (Drooger, 1952, fig. 17, p. 72).
 The following mollusks are in the families covered by chapter A of the present report:


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