GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


 Mollusks.-A few microscopic mollusks were recovered from foraminiferal mudstone and siltstone. Molds of mollusks weather out of limestones in Madden basin. The largest number of species represented by such molds was found at localities 11 and 12. Somewhat calcareous sandstone in the Rio Frijol area contains a few species. The best preservation is shown by silicified fossils collected in the Rio Casaya area (locality 38). These silicified fossils are casts composed of granular silica. They occur in partly silicified limestone and therefore can be extracted by treatment with acid.
 The species listed on p. 21 are represented in the families covered by Chapter A of the present report.
 The mollusks of the Gatuncillo formation include species of Tethyan affinities, an example of which is Velates perversus. Ilannatoma is an American genus, found in the Eocene of Perd, Colombia, and Venezuela, and in the Oligocene of Perd. It is not certain, however, that Hannatoma occurs in the Gatuncillo formation, as the aperture and growth line of the species identified as Hannatoma? cf. H. emendorferi is unknown. Turritella cf. T. carinata, and other species from the Rio Casaya area not included in the preceding list, indicate a middle Eocene age, but the bulk of the fauna suggests late Eocene.
 Echinoids.-Echinoids collected at locality 11 were identified by C. W. Cooke (1948) as Cubanaster acuai, Weisbordella dalli, W. cubae, Schizaster armiger, and Eupatagus clevei. Cubanaster acunai is very abundant in slabs of silty limestone that are strewn about at locality 11 (pl. 4). Incomplete remains of Eupatagus were seen at other places in the southern part of Madden basin. According to Cooke, four of the five species at locality 11 are found in the upper Eocene Ocala limestone of Florida, two in the upper Eocene of Cuba, and one in the middle Eocene of St. Bartholomew.
 Age.-The Gatuncillo formation is considered to be of middle and late Eocene age. The faunal evidence consistently indicates that the greater part of the formation is late Eocene. Contrary to a former opinion (Woodring and Thompson, 1949, p. 228), the formation, perhaps only a small part of it, evidently includes middle Eocene, at least in Madden basin and the Rio Casaya area. Yaberinella jamaicensis was found in two collections at the very base of the formation, but not in other collections. Though that species occurs in both middle and upper Eocene in Jamaica, its apparently more closely restricted range in PanamA, suggests that the basal part of the Gatuncillo is middle Eocene. Unfortunately no other collections of larger

Durham's relassiication ID riaey, y. ., A new family of clypesltroid et oloids: Jour. Paleontology, v. 28, p. 677-684, 3 figs., 1954).


Foraminifera from the basal part of the formation are now available. The collection of mollusks from the Rio Casaya area includes species of middle Eocene affinities, such as Turritella cf. T. carinata, which are not represented in other collections. Stratigraphic control, however, is completely lacking in the Rio Casaya area.
 EOCENE 01R OLIGOCENE SERIES MARINE MEMBER OF BOHIO(?) FORMATION
 Marine strata of early Tertiary age in the Gatun Lake area are tentatively designated the marine member of the Bohio(?) formation, pending further data on their stratigraphic relations. They are thought to represent a marine tongue, or tongues, in the lower part of the essentially nonmarine Bohio formation, which is described on pages 24-28. That interpretation, however, is a matter of inference. It is adopted principally because in one of the outcrop areas the strata include rocks similar to those of the Bohio formation.
 Whatever the stratigraphic relations of the unnamed strata may be, a separate formation name may eventually be preferred for them. As a matter of fact, a name was casually used for them many years ago-a name incorrect in orthography and no longer suitable: Vamos a Vamos beds or Vamos a Vamos formation (Hill, 1898, p. 179, 205).
 Though the thickness and extent of this unit are unknown, the thickness probably is at least 100 meters.

 STRATIGRAPHY AND LITHOLOGY
 Vamos Vamos.-The unnamed marine strata were first observed near a now submerged village on Rio Chagres that had the intriguing name Vamos Vamos. The approximate position of the fossiliferous strata is shown as locality 40 on plate 1. Though the name Vamos Vamos suggests American slang, my colleague G. E. Lewis informs me that "vamos" is a colloquial equivalent of the more elegant "viimonos" and that reiteration for emphasis is common in many languages. The name appears on Garella's 1:200,000 map, prepared in 1844 and published in 1845 (Garella, 1845). Hill had his own hybrid version of the name: Vamos a Vamos (Hill, 1898, p. 179), gallicized to Vamos a Vamos by MacDonald (1919, p. 542).
 The strata described as those at Vamos Vamos actually were exposed in a cut on the southwest side of the French Canal, about 2 kilometers northwest of the place where the canal joined Rio Chagres just upstream from the village of Vamos Vamos. (See map, pl. 1, accompanying publication cited under Bertrand and Ziircher, 1899.) These fossiliferous strata were first mentioned by Chaper (1890, p. 7) and were described by Hill (1898, p. 179-180), Howe (1907, p.


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