Elimia virginica, (GMELIN, 1791)

Strong, Ellen E., 2011, More than a gut feeling: utility of midgut anatomy in phylogeny of the Cerithioidea (Mollusca: Caenogastropoda), Zoological Journal of the Linnean Society 162 (3), pp. 585-630 : 611-612

ELIMIA VIRGINICA (GMELIN, 1791)

Material examined

US: Maryland: Potomac River , C &O National Historic Park, 38°59.55′N, 77°14.57′W ( USNM 1143353 ) .

Description

Marginal fold S-shaped ( Fig. 16A ), terminating at posterior tip of sorting area; oesophageal aperture at tip of marginal fold recurved segment; sorting area rectangular, with slightly curving, pointed posterior tip; left margin of sorting area straight; accessory marginal fold extending from oesophageal aperture, around posterior margin of sorting area, with posterior median depression; large, wedge-shaped sorting area pad present at left posterior end of sorting area; anterior flap, crescentic pads lacking; glandular pad large, flaring posteriorly with broadly rounded posterior end, extending far posterior to gastric shield; paired digestive gland ducts opening at left of glandular pad; crescentic ridge long, extending from oesophageal aperture, curving around posterior end of glandular pad, fusing to side of pad well behind gastric shield above shallow caecum; single, elongate caecal fold opposite posterior glandular pad at right; accessory pads lacking; U-shaped fold present below style sac aperture; typhlosoles unfused.

Remarks

Apart for some minor individual variation, this species is virtually identical to Elimia livescens (Menke, 1830) . The two differ in the configuration of the posterior segment of the accessory marginal fold, which is more similar to Melanopsis praemorsa (see Fig. 12B ) in E. livescens ( Strong, 2005) , with a slight median depression, and intersecting a short, slightly curving fold posteriorly. Additionally, E. livescens is distinguished from E. virginica by the presence of a small accessory pad in the former, which was not mentioned by Strong (2005).

Figures

Figure 12. Midgut anatomy of Melanopsidae. A, Holandriana holandri (ZMB 106.145). B, Melanopsis praemorsa (ZMB 106.066). Scale bars: 1.0 mm; refer to the text for a list of anatomical abbreviations.

Figure 16. Midgut anatomy of Pleuroceridae (A) and Semisulcospiridae (B). A, Elimia virginica (USNM 1143353). B, Semisulcospira libertina (ZMB 102.184). Scale bars: 1.0 mm; refer to the text for a list of anatomical abbreviations.