No description available.

The dislocation etch pits formed on the cleavage surfaces of lithium fluoride in an aqueous solution containing varying concentrations of ferric ions are investigated by electron microscopy. The results obtained reveal the powerful influence of the inhibitor in the stabilisation of kinks and macroledges. There is some evidence for the nucleation of disso­lution at imperfections other than the dislocations. Dissolution spirals are observed in some cases suggesting the presence of helical dislocations in lithium fluoride. / Thesis / Master of Science (MS)

No description available.

Retinal terminal profiles in the goldfish optic tectum were identified electron microscopically after (1) labeling with horseradish peroxidase and (2) in the early stages of degeneration in short‐term eye enucleates. All labeled terminals shared certain common morphological characteristics which were identical to those of a population of terminals in normal tecta. Terminals of this type disappeared 30 days after enucleation of the contralateral eye. Retinal terminal presynaptic profiles were characterized by (1) round and oval synaptic vesicles; (2) mitochondria with irregular, randomly oriented cristae, large intracristal spaces, dilated membrane spaces, and primarily light matrices; (3) a wide range in profile area, 0.06–6.82 μm2; (4) large numbers of synaptic vesicles per profile area 168± 33 synaptic vesicles per μm2; (5) asymmetric synapses; and (6) multiple synaptic contacts (1.46 ± 0.73 per terminal profile). The postsynaptic elements included both dendritic and, less commonly, pleomorphic vesicle‐containing profiles. The majority of postsynaptic dendritic profiles were small (0.01–0.40 μm2). Serial synaptic contacts were occasionally seen. The combination of vesicular and mitochondrial morphology (1 and 2 above) was necessary and sufficient to establish the retinal origin of a terminal, but use of such criteria would underestimate the number of retinotectal terminals by omitting those which did not have a mitochondrion in the plane of section. The number of such terminals was calculated from independent measurements, and the total number of retinal terminal profiles per area of neuropil was estimated.

The ecological distributions of tardigrade species from six sites on Roan Mountain, Tennessee-North Carolina, were determined in a study begun by D. R. Nelson in 1971. Three new species of eutardigrades were discovered in Nelson's study, but remained undescribed. A follow-up to that study was initiated by K.L. McGlothlin in 1988 to determine the long-term stability of tardigrade populations at two of Nelson's original collection sites. Two of Nelson's three new eutardigrade species were rediscovered by McGlothlin, and one new Pseudechiniscus species was found. The description of one of the eutardigrades, Hypsibius roanensis, was published previously. The remaining eutardigrade found during both studies, a new species of Calohypsibius, is described here: Calohypsibius schusteri sp. nov.

No description available.

No description available.

No description available.

A thorough morphological description of Teleoceras material from the Gray Fossil Site, Gray, Tennessee is provided. This is the only record of a browsing Teleoceras and, as a late Hemphillian locality, represents one of the youngest populations. Linear measurements of post-cranial elements indicate proportional differences between Teleoceras from the Gray Fossil Site and those from other Hemphillian localities. These differences are more pronounced in the elements of the forelimb than in those of the hind limb. Statistical analyses of post-cranial elements from 3 Hemphillian species of Teleoceras suggest that these differences should not be used to separate species. However, the elements do typically sort well by fossil locality, which suggests that post-cranial morphology is plastic enough to become modified within a population. Furthermore, dental morphology comparisons with the holotypes of these species indicate that the GFS rhino represents a previously undescribed species.

Here, a morphological description of the extinct meline badger Arctomeles dimolodontus from the Gray Fossil Site (GFS), Tennessee is provided with comparison to extant Meles meles. Originally described solely on upper teeth of a single individual, the recovery of several crania and jaws provides a sample of at least five individuals, affording the largest known fossil sample in North America of the enigmatic Melinae. Examination of A. dimolodontus skull material reveals extreme intraspecific variation in previously identified diagnostic characters, highlighting the need for caution when identifying fossil taxa based on similarly fragmentary remains. Dental variation is likely a result of hypocarnivory, and dentition may have become more complex over time in response to diet. Based on cranial characters, A. dimolodontus appears to be sexually dimorphic, similarly to extant badgers. Arctomeles dimolodontus has a complex auditory region with large bullae compared to M. meles, suggesting relatively heightened auditory sensitivity.