GEOLOGY Mollusks from Culebra formation, exclusive of Emperador limestone member (Neritidae to Turritellidae) 98 99a 99b 99c 99d 9f 99g 99h 100 100b 104b 106 Aeritina (Vitla?) sp Littorina aff. L. angulifera (Lamarck) ---Rissoina (Zebinella?) sp Xenophora sp Hipponix? sp Crepidula sp Calyptraea cf. C. centralis (Conrad) Trochita'? cf. T. trorthiformtis (Born) -Crucibulum sp Natica (Naticarius?) sp -Polinics? sp Neverita? sp -- Sinum sp - Globularia (Globutaria) off. G. fischeri (Dall) -Pachycrommium? cf. P.? trnitatensis (Mansfield) -cf. P. guppyi (Gabb) Turritella (Torcula?) amaras Woodring, n. sp _.- sp --cf. T. subgrundifera Dall venezuelana Hodson.--- ---. rf. T. berjadinensis cocoditana Hodson ---------- 107 1t0 108cl 110 110a 111a 111 112 112a 114 115a 115b 116 -- -- - -- - -xx- -- --- -- --- --- - -- -- -- -- - --- -- - -- -- --- X- _--- --- -- -.-- --+ -- --- --- --- --- -- - -- -- X X X --- --- - - -- -- X - -- -- --- ------- --- --- X X -X -.- X X - - -- X X --- - - - - - --- X ------. X -- -X X X X X --- -- --- X X --X X X -- -- -- .-- X - Collections from the type locality of the Emperador member contain only a few species of mollusks, none of which represents the families described in chapter A of the present report. Limestone in the Las Cascadas area assigned to the Emperador contains Neverita? sp. (localities 119a, 120) and Turritella altilira in the unrestricted sense (locality 120). Echinoids.-Clypeaster lanceolatus and Echinolatpas semiorbis were recorded from the Emperador limestone member by Jackson (1917, p. 490, 498). Mammal.-In 1942 T. F. Thompson found an incomplete mammal bone in the transition zone between the Culebra and Cucaracha formations at locality 110 onthe east side of the canal-the first Tertiary maminal to be found in Panamd. The following comments on this fossil and the drawings by 0. J. Poe reproduced as figure 2 are available through the kindness of R. A. Stirton, of the University of California. The bone found by Mr. Thompson is the distal part (length 78 millimeters) of a metapodial of an ungulate of medium size. It was examined by H. E. Wood, 2nd, who thought it represents a rhinoceros similar to Diceratherium. G. G. Simpson doubted that it is a South American ungulate, but had no material for close comparison with the leontiniids. The apparent rhinoceros affinities seemed to be conclusive until late Miocene leontiniid foot bones, collected by University of California expeditions in 413788-57--4 Colombia, were available for comparison. This material indicates that the metapodial from the Canal Zone may represent a South American leontiniid or a North American rhinocerotid. Despite a search in 1947 and 1949, no additional mammal remains were found at or near locality 110 Age.-Douvilld (1891, p. 499) and 1111 (1898, p. 195), relying entirely on lithologic similarity to lignitic strata in the Eocene of the Gulf states, suggested that the Culebra is Eocene. A review of other age assignments-Eocene, Oligocene, Miocene-would hardly be profitable. It may be pointed out, however, that DouvillS (1898, p. 591) and Bertrand and Zfircher (1899, p. 89, 90), evidently following his advice, thought that small orbitoids in strata that presumably represent the Culebra are reworked. The fossils of the Culebra formation, including the Emperador member, have both Oligocene and Mioeette affinities. The orbitoids (three lepidocycline species of Lepidocclina) point to Oligocene. In fact, some paleontologists consider lepidocycline species to be decisive for an age not younger than late Oligocene. According to Vaughan's data, the corals favor correlation with the Anguilla formation of Anguilla, which contains no orbitoids. The mollusks also favor correlation with the Anguilla and other formations of the same age, 37 X