Heliolitine corals occur in Upper Silurian strata of the topmost Douro, lower Barlow Inlet, and lower Somerset Island formations in the Boothia Uplift region. The fauna includes Heliolites (nine species), Propora (two species), the stelliporellid genera Podollites (three species) and Stelliporella (one species), and the plasmoporid Squameolites (one species). Species present but not previously reported from the region include Heliolites arcuatus Bondarenko, Heliolites uksunayensis Mironova, Stelliporella ilensis Bondarenko, Podollites assitus new species, Podollites parryi new species, Podollites plectilis new species, Propora tubulata (Lonsdale) and an unidentified species of Propora. All species occur in reef and reef-associated facies of open carbonate shelf and ramp settings. In restricted nonreefal carbonate shelf settings, diversity attenuates to a minimum, exemplified by numerically abundant monospecific assemblages of Heliolites uksunayensis. Six of the 16 morphotaxonomic units recognized compare with species reported previously in Silurian faunas of Kazakhstan and Mongolia. Combinations of characters in the species attributed to Podollites support revision of the genus, possibly to include Derivatolites and Tarbagatailites, in a group morphologically intermediate between Stelliporella and Heliolites.

An account of the systematics, biostratigraphy, ecological setting and the biogeographic implications of rugose corals from olistoliths of the Cabrières area is given. Corals of the lower member of the Izarne Formation are dated by conodonts as gronbergi Zone age, and include Lythophyllum sp. indet., Calceola sandalina (Linné), Tryplasma sp. A, Breviphrentis roharti Pedder new species, B. exigua Pedder new species, and Aqishaphyllum sp. A. Corals from the middle member of the formation include Frechocystis pertinax Pedder new genus and species, Calceola sp. undet., Rhizophyllum sp. aff. R. ukalundense Hill and Jell, Tryplasma enorme Pedder new species, Tryplasma sp. A, Breviphrentis sp. A, Platysmatophyllum halleri Pedder new genus and species, Pseudochonophyllum sentum Pedder new species, and Izarneophyllum barroisi (Frech) new genus. No age significant conodont has been recovered from the middle member. However, scutelluid trilobites, which, together with other trilobites, evidently used the underside of Izarne corals for shelter during molting, provide correlation with conodont sequences in the nappe domain to the north and southwest of Cabrières. From this line of evidence, the middle Izarne coral fauna is deduced to be nothoperbonus Zone age. The association of a variety of benthic trilobites, all with large eyes, provides evidence of a photic zone environment for the middle Izarne corals.

Rugose corals from the Izarne Formation belong to the Old World Realm and have nothing in common with similar age Rugosa of the Eastern Americas Realm. This implies that the dissolution of the boundary between these realms, which occurred in the Middle Devonian, did not begin before latest Emsian time.

The most important factor controlling the timing of Phanerozoic mineralogical evolution in the Bivalvia appears to be thermal potentiation of calcite deposition in colder marine and estuarine environments. Cold temperature has promoted mineralogical evolution in the Bivalvia by kinetically facilitating (potentiating) initially weak biological controls for calcite, thereby exposing their genetic basis to natural selection. Calcite has evolved in bivalve shells for a variety of selective advantages, including resistance to dissolution; resistance to chemical boring by algae and gastropods; reduced shell density in swimming and soft-bottom reclining species; enhanced flexibility in simple prismatic shell layers; and fracture localization and economy of secretion in association with certain foliated structures.

Endogenous calcite in bivalve shells varies from biologically induced to weakly and strongly biologically controlled. Biologically controlled calcite generally first appears in bivalve shells as an impersistent component of the outer shell layer, only later, in some groups, expanding to include the entire outer and then part or all of the middle and inner shell layers. The initial stages of mineralogical evolution are shown by certain modern Mytilidae, Veneridae and Petricolidae. In the latter two families, the calcite occurs as conellae in the outer part of the outer shell layer. Calcitic conellae in the inner shell layer of Pliocene Mercenaria are not barnacle plates, as previously indicated, but endogenous calcite comparable in origin to other venerid conellae. Their occurrence in Mercenaria may reflect thermal potentiation of weak biological controls for calcite, as well as local detachment of the secretory mantle epithelium near the pallial and adductor musculature.

Twenty species of bivalves are described from the Ixtaltepec Formation, in Nochixtlán, México. Representatives of the genera Parallelodon, Myalinella, Septimyalina, Leptodesma, Pterinopectinella, Aviculopecten, Limipecten, Streblopteria, Euchondria, Schizodus, Permophorus, Astartella, Edmondia, and Ectogrammysia are present. These species, and those of nuculoid bivalves previously described from the same formation, include infaunal and epifaunal forms that lived in shallow marine environments from Morrowan to Desmoinesian ages. Pennsylvanian bivalves from Nochixtlán are related to the Midcontinent and Appalachian faunas, which indicate that there was an oceanic connection between these areas in a latitudinal belt near the equator that partially covered southeastern Mexico.

Three new species of the shallow-marine, warm-water bivalve Plicatula are reported from the upper Paleocene Santa Susana Formation of southern California. Plicatula simiensis new species is from the middle part of the formation on the south side of Simi Valley and occurs as a displaced specimen in deep-marine turbidites. Plicatula lapidicina new species and P. trailerensis new species are both from coralline-algal-rich muddy siltstone just beneath a nearshore, coralline-algal limestone interval in the upper part of the formation in the Santa Ynez Canyon area, east-central Santa Monica Mountains. These three new species represent the first late Paleocene records of genus Plicatula on the west coast of North America and the first Paleocene records of this genus in southern California.

Trilobites assigned to 14 genera and 14 species are reported from basal part of the Deadwood Formation in the Black Hills of South Dakota. Six additional taxa are left in open nomenclature. One new species, Cedarina dakotaensis, is described. These trilobites are assigned to a new zone, the Cedarina dakotaensis Zone, named after the most abundant trilobite species.

Species of Cedarina and Modocia are the most abundant in the Cedarina dakotaensis Zone, accompanied by less common specimens of species of Arapahoia, Menomonia, Hardyoides, Welleraspis, Kormagnostus, and Kingstonia. Cedarina dakotaensis and Modocia centralis are the most abundant species in the nearshore sandstone lithofacies, whereas Arapahoia spatulata is the predominate taxon in the offshore limestone lithofacies.

The fauna of the Cedarina dakotaensis Zone (which lacks species of Cedaria) occupies the biostratigraphic interval of the traditional Cedaria Zone of the Marjuman Stage. Trilobites from the Cedarina dakotaensis Zone can be used to correlate the basal part of the Deadwood with coeval strata elsewhere in North America.

Rare to abundant specimens of Moorites Coryell and Billings, 1932, and Discoidella Croneis and Gale, 1938, have been recovered from 13 Pennsylvanian stratigraphic units in the Appalachian basin. Eight species of Moorites, including the new species M. sturgeoni, M. ornatus, M. percultus, and M. erugatus, are recognized. Discoidella is represented by D. lingulata Cooper, 1946. Moorites hewetti Coryell and Billings, 1932, is recognized as the type species of Moorites. An ontogenetic series of M. percultus illustrates changes in shape and ornamentation. Increase in complexity of ornamentation from Lower to Upper Pennsylvanian provides a basis for specific identification.

Middle Pennsylvanian, Atokan and Desmoinesian, crinoids and echinoids are described from the Belden and Minturn Formations of the Central Colorado Trough. The echinoderms from the Minturn Formation were living in an active intermontane trough setting. They are found in two environments, on the flanks of phylloid algal reefs and in patches on abandoned delta lobes on the gently sloping substrate. Faunas are dominated by cromyocrinids and are similar to stable platform Terrigineous Facies Belt faunas of the Midcontinent.

New species described are Dicromyocrinus beldenensis, Neoprotencrinus rockensis, and Sciadiocrinus wipsorum. Goleocrinus, and the columnal genera Blothronagma, Cyclocaudex, and Platyplateium are reported for the first time from the Minturn Formation. The columnal taxa Blothronagma cinctutum and Floricyclus angustimargo are believed to be cromyocrinids. B. cinctutum may be synonomous with Synarmocrinus molasensis, and Floricyclus angustimargo may be synonymous with Ulocrinus rockymontanus.

On the basis of morphological and taphonomic study of a large sample population, Miaohephyton bifurcatum Steiner, emend. from the terminal Proterozoic Doushantuo Formation (600-550 Ma), South China, is interpreted as algal fragments shed from their parent thalli for reproductive or environmental reasons. Characters such as regularly dichotomous, multicellular thalli with forked tips, apical and intercalary meristematic growth, abscission structures, and possible conceptacles collectively suggest an affinity with the brown algae, in particular the order Fucales. In conjunction with reports of xanthophyte fossils in older Neoproterozoic rocks, this reinterpretation of Miaohephyton bifurcatum indicates that photosynthetic stramenopiles (chrysophytes, synurophytes, xanthophytes, phaeophytes, and diatoms; or chromophytes sensu stricto) diversified during the Neoproterozoic Era along with the red and green algae. This, in turn, suggests that the secondary endosymbiosis that gave rise to the photosynthetic stramenopiles took place relatively soon after the evolutionary transformation of cyanobacteria to rhodophyte plastids.