Since Haeckel's Biogenetic Law (‘ontogeny recapitulates phylogeny’) fell into disrepute early in the twentieth century, there has been intermittent debate, particularly in recent years (de Beer, 1958; Gould, 1977; Alberch et al., 1979; Alberch, 1980; Bonner, 1982; McNamara, 1982a), on the nature of the relationship between an individual's development and phylogenetic history. Important questions under discussion include the following: If a strong causal relationship does exist, what is its nature? How does it work? What is its importance in evolution? How can it be recognized in the fossil record?

Neotryplasma floweri n. sp. is an epizoic solitary rugose coral characterized by two orders of perforate, monacanthine, carinate septa, a complex axial structure of septal lobes and lamellae, and a well developed broad dissepimentarium. It occurs in the Late Ordovician (late Edenian to earliest Maysvillian; late Caradoc) Upham Dolomite Member of the Second Value Dolomite, Montoya Group, at El Paso, Texas, U.S.A. Neotryplasma Kaljo, 1957, also includes two Late Ordovician species from the Estonian S.S.R. and one from the late Middle and Late Ordovician of the northern and middle Ural region, U.S.S.R. This genus is assigned to the Neotryplasmatidae n. fam., which is placed in the Suborder Monacanthina Neuman, 1984.

Neotryplasma appears to be closest to Sumsarophyllum Lavrusevich, 1971a, from the Late Ordovician of the Zeravshan-Gissar region, U.S.S.R. This is noteworthy because Erina (1978) and Erina and Kim (1980) suggested that the latter may be a scleractinian coral of the Order Fungiida Verrill, 1865. The rugosan mode of septal insertion has been confirmed in Neotryplasma. N. floweri seems to bear close resemblance to a poorly known Ordovician coral, Cyathophyllum (?) kjerulfi Kiaer, 1932, from Caradoc–Ashgill strata in the Trondheim region of Norway.

Acidolites Lang, Smith and Thomas occurs in upper Middle and Upper Ordovician, Lower and lower Middle Silurian rocks of Ontario and Quebec. On Anticosti Island, Quebec, the genus is represented by A. tenuis (Billings) in the Upper Ordovician (Gamachian) Ellis Bay Formation; the new species A. arctatus, A. compactus and A. helianthus in the Ordovician–Silurian boundary beds at the top of the Ellis Bay Formation; the new species A. arctatus, A. compactus and A. lindströmi in the lower Llandoverian Becscie Formation; A. arctatus in the mid-Llandoverian Gun River Formation; and an unnamed species in the upper Llandoverian Jupiter Formation. The lower Llandoverian Clemville Formation of the Gaspé Peninsula, Quebec, contains Protaraea clemvillensis Parks, now considered to be Acidolites. The upper Middle to lower Upper Ordovician Cobourg Formation near Ottawa, Ontario, contains A. cf. arctatus, formerly included in Protaraea vetusta (Hall). The lower Wenlockian Amabel Formation in southern Ontario contains a species of Acidolites as yet unnamed.

Twenty-two specimens of Thuliocyclus prominens, a new palaeocyclid rugose coral genus and species, on a loose slab presumably from the lower Pridolian Barlow Inlet Formation at Cape Rescue on Cornwallis Island, Northwest Territories, Canada, provide a good growth series from neanic to ephebic stages. The new genus shares morphological characteristics with both typical Silurian Palaeocyclidae and more advanced Devonian Hadrophyllidae.

Acheilus Clark, 1924, is a kingstoniid trilobite, not a catillicephalid or an unrecognizable genus as previously thought. The catillicephalid Theodenisia Clark, 1948, is here restricted to those species in which the axial furrows terminate at the 4s furrow and which lack a preglabellar furrow. Peracheilus n. gen. is proposed as a replacement name for the catillicephalid Acheilus Raymond, 1924. It includes those species previously assigned to Theodenisia in which the axial furrows continue past the 4s furrow to join a narrow preglabellar furrow. Acheilus, Theodenisia, and Peracheilus occur in the Late Sunwaptan of North America; Theodenisia also occurs in the early Ibexian.

The type species of the eurekiid trilobite Corbinia Walcott, C. horatio Walcott, 1924, possesses very short palpebral lobes located opposite 2p glabellar lobe. The palpebral lobes of species of Eurekia Walcott and of Corbinia apopsis Winston and Nicholls, 1967, are considerably longer and located opposite 1p and 2p glabellar lobes. Corbinia is here restricted to the type species, and C. apopsis is assigned to Eurekia. Corbinia horatio occurs in the Basal Silty Member of the Survey Peak Formation of southern Alberta and appears to be confined to the lower part of the Eurekia apopsis Subzone of the Saukia Zone (basal Ibexian).

A new medusoid hydrozoan, Plectodiscus malayites n. sp., belonging to the Family Velellidae is described from Carboniferous rocks of the Malay Peninsula. They are preserved as flattened internal float structures or pneumatophores and are the first examples from this part of the world. In contrast to other occurrences, the great abundance of these sailed organisms suggests that, like extant species of Velella, these organisms were an important component of the pelagic fauna and were at least locally abundant in open seas of the late Paleozoic.

Six Early Silurian Rhodocrinitacea (Crinoidea, Camerata) are recognized from the Brassfield Formation of Ohio. Previously only a single Early Silurian rhodocrinitacean was known. The new forms include Kyreocrinus constellatus n. gen., n. sp.; Rhachicrinus wrighti n. gen., n. sp.; Silfonocrinus siluricus n. gen., n. sp.; Stereoaster squamosus Foerste; Xysmacrinus greenensis n. gen., n. sp.; and Turbocrinus punctum n. gen., n. sp. Rhachicrinus and Silfonocrinus are assigned to the Opsiocrinidae, which previously included two Devonian genera; Turbocrinus is assigned to the Anthemocrinidae; and Kyreocrinus, Stereoaster and Xysmacrinus are assigned to the Rhodocrinitidae.

The Opsiocrinidae are thought to be derived from the Reteocrinidae; and a possible basis for subdividing the Rhodocrinidae is proposed, based on the arms, plating in regular interrays, presence of median ray ridges and calyx shape.

Rudists arose in the Late Jurassic and survived for nearly 100 m.y. before becoming extinct at the end of the Cretaceous. Over this interval they diversified gradually during the Late Jurassic and Early Cretaceous, rapidly in the mid-Cretaceous, then more slowly in the Late Cretaceous. Total rates of origination and extinction during the Late Jurassic and Early Cretaceous were uniform and comparable to those reported for other groups. The Late Cretaceous, however, was characterized by high and widely fluctuating total origination and extinction rates. Per taxon rates reveal a similar pattern except for high and variable rates in the Jurassic. The number of genera increased from the Oxfordian to a peak in the Cenomanian, decreased in the Turonian and Coniacian coinciding with a minor mass extinction event, and rose to a zenith in the Maastrichtian. Unlike other groups investigated, the rudists were at their highest level of diversity immediately prior to their disappearance.

Rudist genera survived for a mean of 12 m.y., whereas families survived for a mean of 48 m.y. Survivorship curves for generic cohorts, based upon survival of all rudist genera that evolved during each stage, exhibit a concave shape when the effects of mass extinction and variance at low diversities are considered. Causal factors involved in the final disappearance of the rudists remain unclear; however, their tropical provinciality in the Late Cretaceous contributed to their vulnerability to mass extinction.

A new full description of the bivalve Shikamaia akasakaensis Ozaki (genotype species of Shikamaia) is presented, providing the first documentation of its hinge and ligament, and resolving many uncertainties about Shikamaia, the first described genus of the Permian bivalve family Alatoconchidae. The genus Shikamaia has a unique ligament, modified from typical duplivincular ligaments in occupying only half of the cardinal area, and having ligament sheets that extend themselves towards the beak with continued growth. This ligament is strikingly different from the ligaments of other alatoconchid genera. All alatoconchids are believed to have a common ancestry, but the magnitude of difference in their hinges warrants dividing the family into two subfamilies. The subfamily Saikraconchinae is erected new.

Three late Devonian ammonoid-bearing levels are described from the area of Cleveland, Ohio. These appear to represent the German Platyclymenia, Clymenia and Wocklumeria Stufen, clear evidence for which has been lacking previously in eastern North America. The lowest level, around the base of the Cleveland Shale, yields Sporadoceras, Cyrtoclymenia, Platyclymenia and a new species, Pleuroclymenia (?) ohioense. The middle level, near the top of the Cleveland Shale, bears Cymaclymenia, Sporadoceras and Prionoceras. The highest level, just above the base of the Bedford Shale, has Prionoceras quadripartitum. This species, and a fauna of the basal Bedford, have been located also in the area of Columbus, Ohio. An Epiwocklumeria (?) sp. is recorded from Indiana. Attention is drawn to the international importance of the late Famennian and Lower Carboniferous ammonoid sequence which can now be recognized in Ohio.

Late Ordovician radiolarians are described from allochthonous limestone breccia deposits of the graptolitic Malongulli Formation of central New South Wales. Included among the forms are the new ‘palaeoactinommid’ genus Kalimnasphaera with new species K. maculosa, the new entactiniid species, Entactinia subulata, and the new anakrusid species, Auliela taplowensis. A number of other entactiniids and the first recorded Ordovician ‘rotasphaerids’ are placed in open nomenclature. Graptolite faunas of the Malongulli Formation indicate that the deposits range in age from the Eastonian Zone of Dicranograptus hians kirki to the Bolindian Zone of Climacograptus uncinatus, that is, from latest Caradoc to early or middle Ashgill in age. This is only the second known well-preserved radiolarian assemblage to be illustrated from Late Ordovician (late Caradoc–Ashgill) successions, and the earliest known from Australia. The radiolarians typically occur in tabularly shaped, laminated lime-mudstone clasts with an abundance of siliceous sponge remains. These clasts appear to be formed from peri-platform ooze of the ‘deeper-water’ slope facies, which became incorporated in debris flows moving into the adjoining basin.

Amphissites insignis Croneis and Thurman, 1939, is a readily identifiable ostracode species because of the unique configuration of carinae and ridges on the surface of the valves. The species had adapted to both shale and limestone environments of deposition, has a wide geographic distribution in the United States (Alabama, Arkansas, Illinois, Montana, Nevada, Tennessee, and Texas), and is confined to the uppermost part of the Chesterian Series (foraminiferal zones 18 and 19). The description of this species is amended and specimens are illustrated for the first time from Nevada, Montana, Arkansas, and Tennessee, indicating that the species is a biostratigraphic indicator of the uppermost part of the Chesterian sedimentary sequence. Ontogenetic development of A. insignis is reconstructed. A. sp. 1 (Late Mississippian) and A. sp. 2 (Early Pennsylvanian) are illustrated in open nomenclature.

Haystack Cave, Gunnison County, Colorado, has provided the first collection of vertebrate remains from the Pleistocene (Rancholabrean) of western Colorado. Two carbon 14 analyses of bone apatite have produced dates of 14,935 ± 610 and 12,154 ± 1,700 years B.P. for this assemblage. This fauna, in conjunction with pollen studies, indicates the Gunnison Basin was largely unforested grassland/sagebrush shrubland in the lower basin, with open coniferous forests extending to the edges of the basin, during the late Pleistocene. The fauna also extends the known Pleistocene range of Lagurus curtatus, Phenacomys intermedius, Spilogale putorius, and Acinonyx trumani.

The Mississippian was a time of widespread diversification of pelmatozoan echinoderms in the United States. The crinoids and blastoids were diverse and abundant in a variety of geologic settings. Most of the Osagean occurrences of blastoids are associated with platform carbonates such as the Burlington Limestone. These blastoids lived in association with a crinoid community dominated by camerate crinoids. Blastoids also lived in coeval Osagean deltaic environments such as the Borden Delta but were less diverse and abundant.

Fossiliferous Late Silurian strata have not previously been recognized in the folded Appalachians south of central Virginia (Berry and Boucot, 1970). In this note, we report that the Red Mountain Formation at two localities in northern Alabama (Sparks Gap and Clear Branch Gap in Red Mountain near Birmingham, Figure 1) has yielded fossils like those of the Cobleskill Limestone (Pridolian, latest Late Silurian). The Red Mountain Formation in this area consists of interbedded sandstone, mudstone, claystone and limestone; some beds are hematitic and most are intensely weathered. The critical fossils are the brachiopod Eccentricosta sp. cf. E. jerseyensis (Weller, 1900) and the ostracode Welleriopsis? sp. aff. W.? pustulosa Berdan, 1972. The Eccentricosta beds at Sparks Gap and Clear Branch Gap are assigned to the Red Mountain because they are lithologically similar to lower beds in the formation. Thus the youngest part of the Red Mountain Formation in the Birmingham area is of Late Silurian, Pridolian, age. At Sparks Gap, underlying beds yielded Late Silurian corals that are not assigned to a faunal zone.