Microstructure and crystallographic texture data in modern giant clam shells (Tridacna squamosa and Hippopus hippopus).

This article provides novel data on the microstructure and crystallographic texture of modern giant clam shells (Tridacna squamosa and Hippopus hippopus) from the Coral Triangle region of northeast Borneo. Giant clams have two aragonitic shell layers-the inner and outer shell layer. This dataset focuses on the inner shell layer as this is well preserved and not affected by diagenetic alteration. To prepare samples for analysis, shells were cut longitudinally at the axis of maximum growth and mounted onto thin sections. Data collection involved scanning electron microscopy (SEM) to determine microstructure and SEM based electron backscatter diffraction (EBSD) for quantitative measurement of crystallographic orientation and texture. Post-acquisition reanalysis of saved EBSD patterns to optimize data quality included changing the number of reflectors and band detection mode. We provide EBSD data as band contrast images and colour-coded orientation maps (inverse pole figure maps). Crystallographic co-orientation strength obtained with multiple of uniform density (MUD) values are derived from density distributed pole figures of indexed EBSD points. Raw EBSD data files are also given to ensure repeatability of the steps provided in this article and to allow extraction of further crystallographic properties for future researchers. Overall, this dataset provides 1. a better understanding of shell growth and biomineralization in giant clams and 2. important steps for optimizing data collection with EBSD analyses in biogenic carbonates.

A further review of European Magelonidae (Annelida), including descriptions of Magelona equilamellae and Magelona filiformis.

Following on from the partial review of European Magelonidae by Fiege et al. (2000), a dichotomous identification key, a table of characters and images of all nine known European magelonid species are provided. Magelona equilamellae is redescribed highlighting several features not reported originally by Harmelin. Notably the thoracic neuropodial lamellae, which are initially prechaetal but become distinctly postchaetal by chaetiger 7, an additional character allowing separation from the morphologically similar Magelona alleni. Records suggest that M. equilamellae is a Mediterranean species, more commonly occurring in shallow, transitional waters. Several new characters for Magelona filiformis are additionally highlighted as well as a number of corrections to the existing description, including the number of prostomial ridges, presence of abdominal lateral pouches, morphology of chaetiger 9, and the presence of smaller abdominal hooded hooks adjacent to lateral lamellae. The first image of M. filiformis minuta is provided, and its synonymy with M. filiformis further supported.

Redescription of Magelona minuta Eliason, 1962 (Annelida), with discussions on the validity of Magelona filiformis minuta.

Since Magelona minuta was described in 1962 our understanding of the key features required to distinguish between magelonid species has increased. The original description contains only four illustrations and vital information on many key characters is not included. This re-assessment of the holotype and material from the type locality includes several features not previously described, specifically related to thoracic and abdominal lamellae. Comparative material from Britain and the Southern Irish and Celtic Seas is examined, adding information on the posterior region. Diet is discussed based on the gut contents of a specimen originally identified by Eliason. Information on numbers of thoracic chaetae and the angle between teeth of abdominal hooded hooks for several magelonid species is investigated. The validity of the dwarf species Magelona filiformis minuta is herein examined.