W. P. Woodring
1973
<p>Chapter E adds 112 described species and subspecies (a few briefly described) to the some 440 covered in preceding chapters : 27 additional gastropods, 18 scaphopods, and 67 pelecypods in 10 families. It is estimated that about 125 species are to be added in chapter F, the final chapter.</p><p>The Arcidae is by far the largest family in the pelecypods so far studied : 30 species in six genera. The genus <i>Anadara</i> is the largest in that family : 25 species, representing the subgenera <i>Hawaiarca?</i>, <i>Rasia, Tosarca, Grandiarca, Potiarca</i>, and <i>Cunearca</i>. <i>Potiarca</i>, based on a living western Pacific species, is adopted for many American species heretofore assigned to <i>Cunearca</i>.</p><p>Eighteen of the 27 additional gastropods were found at a new locality in the late Eocene part of the Gatuncillo formation. They 'are assigned to 16 genera, 14 of which are not represented at other Gatuncillo localities. The genera include <i>Faunus, Turnpanotonos</i>, and <i>Bezaneonia</i>, which are rare in America, and the rare endemic American genus <i>Harrisianella</i>.</p><p>The marine member of the Bohio (?) formation is now assigned to the late Eocene, instead of late Eocene or early Oligocene—the only change in age assignment. Eocene affinities are especially strengthened by the presence of <i>Samanoetia samanensis</i> and <i>Volvariella?</i>, if indeed the unnamed species represents that genus, as seems likely. Both the marine member of the Bohio( ?) and the late Oligocene part of the Bohio contain early small species of <i>Anadara</i>, subgenus <i>Rasia</i>.</p><p>The fossils from the moderately deep-water facies of the late Oligocene Caimito formation include the earliest hexagonal <i>Dentalium</i> of the subgenus <i>Dentalium</i> s.s., from the American mainland, and a widespread and abundant species of the essentially deep-water subgenus <i>Fissidentalium</i>.</p><p><i>Anadara chiriquiensis chiriquiensis</i>, a relatively small form of the subgenus <i>Grandiarca</i> that is widely distributed in the Miocene Caribbean province, occurs in the Culebra formation. For the most part it indicates brackish water.</p><p>Among the fossils from the La Boca formation proper, <i>Cyphoma</i> aff. <i>C. intermedia</i> is the earliest representative of an endemic American genus, and <i>Isognomon mimeticus</i>, a remarkable, narrowly mytiliform species is the type of the new subgenus <i>Mimonion</i>. Both the Culebra and La Boca, both of early Miocene age, contain predecessors of Gatun species.</p><p>As in other chapters, the largest number of species is from the middle Miocene Gatun formation: 50 species. <i>Bailya crossata</i> is the first Tertiary species of the genus from the Caribbean region, and the earliest now known. A bizarre, incomplete gastropod is described as xancid?, genus?. The Gatun contains 13 of the 24 species of <i>Anadara</i> and half of the 12 species of the subgenus <i>Rasia</i> of that genus. In consideration of two battered and worn specimens of a large form of the subgenus <i>Grandiarca</i>, identified as <i>Anadara grandis patricia?</i>, the similar Tertiary forms in the Caribbean region are reviewed and divided into a brackish-water group and a marine group. The Gatun fauna now totals some 330 species. </p>
application/pdf
10.3133/pp306E
en
U.S. Government Printing Office
Geology and paleontology of Canal Zone and adjoining parts of Panama: Description of Tertiary mollusks (additions to gastropods, scaphopods, pelecypods Nuculidae to Malleidae)
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