Section of marine member of Bohio(?) formation on north coast of Trinidad Island


113; 1908, p. 219), and MacDonald (1919, p. 542). According to these descriptions, the strata dipped toward the northwest and consisted of dark tuffaceous silty sandstone, containing practically black calcareous concretions, and small-pebble conglomerate. Fossils were found in the calcareous concretions and also in the sandstone. MacDonald reported a thickness ol 95 feet (29 meters) at locality 40.
 Hill thought the strata at Vamos Vamos to be younger than the foraminiferal marl exposed farther east (Hill, 1898, p. 179), and so did Bertrand and Zircher (1899, p. 88). (The foraminiferal marl, now submerged, is presumed to be part of the Caimito formation.) Howe concluded that the coarse conglomerate and volcanic breccia at Bohio, still farther east, and the strata of finer grain at Vamos Vamos represent different faces of the same formation: the Bohio formation (Howe, 1908, p. 221). MacDonald and Vaughan assigned the strata at Vamos Vamos to the Gatun formation (MacDonald, 1919, p. 542). Though little data on the structure and stratigraphy of the marine member of the Bohio(?) formation are now available, that unit seems to be exposed on an anticline, as suggested on plate 1.
 Palenquilla Point.-When Mr. Thompson was reminded of the record of dark fossiliferous calcareous concretions at Vamos Vamos, he remembered that he had seen such concretions near Palenquilla Point, which is close to the submerged Vamos Vamos locality. Tuffaceous siltstone, tuffaceous mediumn- and coarsegrained sandstone, and lenses of conglomerate made up of basaltic pebbles, cobbles, and boulders are exposed at scattered localities on the east side of the peninsula ending at Palenquilla Point. The coarse basaltic fragments generally have a maximum diameter of 10 centimeters, exceptionally 30 centimeters. Loose dark fossiliferous calcareous concretions were found at the edge of Gatun Lake at locality 41 and in place in medium-grained sandstone halfway between that locality and Palenquilla Point. At other places mediumgrained sandstone contains molds of mollusks. The basaltic conglomerate suggests the Bohio formation. Whether these marine strata will be found in an extensive area south and southwest of Palinquilla Point, as suggested on plate 1, remains to be determined.
 Trinidad Island.-The same stratigraphic unit forms Trinidad Island. The following section is exposed on the north coast of the island:


Siltstone, sandy. Locality 42c, 4.5 meters above base-.. Sandstone, ledge-forming, silty, medium-grained, calcareous,
 containing few pebbles, few worn small heads of calcareous algae, and worn shell tips of Turritella.
 Locality 42b -- - - - - - - - 
Siltstone, sandy. Locality 42; locality 42a represents a
 thin calcareous layer ----_ --- -_--- -- -----T hickness of section ------ _---- _--- _-_-_-.---


Meters
 6


3 10


 FOSSILS AND ACE
 Larger Foraminifera.-No Foraminifera of any kind are in the collections from Vamos Vamos and none were observed in the exposures near Palenquilla Point. The following larger Foraminifera were identified by Cole in two collections from Trinidad Island:

Larger Foraminifera from marine member of Bohio(?) formation, Trinidad Island


 [Cole, 192 (193), p.51

Operculinoides jacksonensis (Gravell and Hana)....
 .ugteri Vaughan and Cole ----.------trinitatensis (Nuttall)..- .- ..---.-.. -------Nummulites I striatoreticulatus (L. Rutten) Fabiania cubensis (Cushman and Bermddez) Lepidocyclina (Pliolepidina) macdonaldi Cushman(Pliolepidina) pustulosa H. Douvilli-..
 pustulosa tobleri H. Douvill6-.----I Cited by Cole as Camerina.


Lecalttites
42 420 X X X X X X


 Cole pointed out that all the larger Foraminifera collected at Trinidad Island are found elsewhere in deposits of late Eocene age; in fact, all except two (Operculinoides kugleri and 0. trinitatensis) are found in the Gatuncillo formation. Moreover two (Fabiana cubensis and Lepidocyclina pustulosa) occur in the middle Eocene, but none in the early Oligocene.
 Mollusks.-A collection of mollusks from Vamos Vamos was forwarded to the U. S. National Museum by Alexander Agassiz in 1891. Other collections were made by Hill and by Vaughan and MacDonald. All these collections presumably represent the same general locality. For some reason Hill sent in three lots that have different field numbers. Dall used specimens from the Agassiz and Hill collections to describe four species he named Glyptostyla panamensis, Mactra (Mactrella?) dariensis, Cardiue (Fragum) gatunense, and Pitaria (Lamelliconcha) hilli in his monumental


GEOLOGY


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