gamma-Aminobutyric acid (a simple amino acid and potent neurotransmitter in human brain and other tissues of higher animals) and certain of its congeners rapidly and synchronously induce planktonic larvae of the red abalone, Haliotis rufescens, to settle and commence behavioral and developmental metamorphosis. These naturally occurring inducers of algal origin apparently are responsible, in part, for the substrate-specific recruitment, induction of settling, and the onset of metamorphosis of abalone and other planktonic larvae upon specific algae which provide naturally favorable habitats for the young of these species in coastal waters. These observations provide a convenient experimental model for further analysis of the basic molecular mechanisms by which environmental and endogenous factors control the recruitment and development of planktonic larvae. Halogenated organic pesticides significantly interfere with larval settling, as quantified in a new bioassay based upon these findings.

Addition of hydrogen peroxide to seawater causes synchronous spawning in gravid male and female abalones, and certain other mollusks as well. This effect is blocked by exposure of the animals to aspirin, an inhibitor of the enzyme catalyzing oxidative synthesis of prostaglandin endoperoxide. Hydrogen peroxide activates this enzymatic reaction in cell-free extracts prepared from abalone eggs (a very rich source of the prostaglandin endoperoxide synthetase); this effect appears to reveal a fundamental property of prostaglandin endoperoxide synthesis. Applicability of these findings to both mariculture and medical purposes is suggested.

Pa<"e FIGURE 1. Index map showing the principal mountain ranges in the Great Basin region in northwestern Utah ___ /2 2. Sketch map of the Oquirrh Mountains and South Mountain showing the locations of the Rogers Canyon, Bingham, and Curry Peak sequences _____.__________________________________ 3 3. Generalized columnar sections of the Rogers Canyon and Bingham sequences in the Oquirrh Mountains_ 4 4. Sketch map of the Oquirrh Mountains showing location of type and reference sections _______ _ _ 5 5. Columnar sections showing the development of upper Paleozoic rock-stratigraphic divisions in the Bingham sequence ________________________.___________________________________ 6 6. Columnar sections showing the development of upper Paleozoic rock stratigraphic divisions in the Rogers Canyon sequence __________________._____________________________________ 8 7-12. Photographs of: 7. Typical exposures of Rogers Canyon sequence _____________________ _ 12 8. General features of the lithology of the lowermost part of the Lake Point Limestone _ __ __ ]"3 9. The upper two-thirds of Erda Formation and the basal part of Kessler Canyon Formation _ 15 10. Typical exposures of reference section of the West Canyon Limestone and the basal portion of the Butterfield Peaks Formation in Soldier Canyon __________________-__________ 24 11. Typical exposures of the middle part of the Butterfield Peaks Formation at the head of White Pine Canyon tributary of Middle Canyon __.________________________________ _ 27 12. Typical exposures of the Jordan (limestone) marker bed (a thick cherty limestone) within the base of the Clipper Ridge Member of the Bingham Mine Formation at the type locality of the member in Middle Canyon ______-______________________________ _ 28 13.

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