The characteristics of the research area are in brief as follows: Rancho Grande is located in north-central Venezuela (10° 21' N. Lat., 67° 41' W. Long.), 80 kilometers west of Caracas, at an elevation of 1,100 meters in the undisturbed montane rain forest which covers this part of the Caribbean range of the Andes. Adjacent ecological zones include seasonal forest, savanna, thorn woodland, cactus scrub, the fresh-water lake of Valencia and various marine littoral zones. The Rancho Grande area is generally subtropical, being uniformly cool and damp throughout the year because of the prevalence of the mountain cloud cap. The dry season extends from January into April. The average humidity during the expeditions, including parts of both dry and wet seasons, was 92.4%; the average temperature during the same period was 18° C. ; the average annual rainfall over a five-year period was 174 cm. The flora is marked by an abundance of mosses, ferns and epiphytes of many kinds, as well as a few gigantic trees. For further details, see Beebe and Crane, Zoologica, Vol. 32, No. 5, 1947. Unless otherwise stated, the specimens discussed in the present paper were taken in the montane cloud forest zone, within a radius of one kilometer of Rancho Grande.] CONTENTS.

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The principal elements of fighting and display in the genus Uca are surveyed from the point-of-view of their apparent evolutionary origins. The components include combat behaviour between males, threat postures, acoustic signals and visual displays. The latter are characterized by rhythmic motions of the large cheliped and other appendages. Combat between males is highly ritualized, with morphological and behavioural deterrents to maximum intensity. When the deterrents are effective the fights are usually without noticeable results. Although serious injury virtually never occurs, when the deterrents are inadequate the loser sometimes gives up his burrow and occasionally does not court for varying periods thereafter. Combat seems to have evolved directly from the decapod motion of grasping combined at low intensities with an appeasement element in which the major cheliped—a releaser of aggressive behaviour—is turned away from the opponent. Threat postures are primarily intention motions of fighting. Both in the burrows and occasionally on the surface stridulation and other acoustic signals are used in threat, courtship or both. Unlike combat behaviour and threat postures, visual display is species-specific. The twenty-odd elements most often occurring in both acoustic and visual display seem clearly to be derived chiefly from feeding, cleaning and threat movements, usually through the intermediary of displacement activities; sometimes the display elements apparently evolved from conflict between feeding and threat tendencies and sometimes from intention motions. Even in species with the most advanced displays, ritualization of some elements is often only partly or temporarily achieved, while the corresponding displacement motion, unaltered and uncomplicated, is frequently elicited. Parallelisms are evident between the courses of evolution in the social behaviour of fiddler crabs and vertebrates.

The Middle Jurassic (Bajocian-Bathonian) Beryl Formation of the Beryl (Bravo) Field (Viking Graben), has been produced since 1979 and contains estimated remaining reserves of 180 x 10 6 BBL oil. Previous studies of this deltaic/shallow marine succession have defined five reservoir units. Production characteristics indicate that this lithostratigraphically-based zonation scheme does not adequately define reservoir flow units and constrain sweep efficiency. Here, a more refined reservoir zonation is used to form the basis for an upgraded reservoir simulation model.High density well coverage (50 wells) in the Beryl Bravo area allows the construction of a high resolution reservoir zonation scheme within the main producing interval of the Beryl Formation: Unit 3. The scheme is based on integration of sedimentology, ichnology, biostratigraphy, dynamic data and well log character. Nine reservoir zones (consisting of nine genetic sequences) have been defined and confirmed and are supported by drilling and production data.The complex reservoir zonation scheme is based upon the recognition of regionally extensive marine/ brackish mudstones which, in many cases, form traceable pressure barriers across tilted fault blocks. This framework has allowed subdivision into 3 to 25 m thick correctable units. Individual units record the progradation and transgression of tide-dominated deltaic deposits. Variations in the thickness and development of these units result from sedimentation in actively subsiding half-graben that were subject to regionally extensive base-level changes. The integrated approach taken here has substantially improved the understanding of the architecture and production characteristics of the Beryl Formation.

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