Adula H. Adams & A. Adams, 1857

Kleemann, Karl, 2007, Catalogue and bibliography of Recent and fossil Botula (Bivalvia: Mytilidae), Zootaxa 1508, pp. 1-48 : 5

Adula H. Adams & A. Adams, 1857

( Fig. 1 )

Type species. Mytilus soleniformis Orbigny, 1846 , by monotypy.

Diagnosis. Shell elongate, sub-cylindrical, umbones distinctly off anterior end, a diagonal line or shallow keel separating antero-ventral from postero-dorsal “triangle” of shell surface. Ventral margin usually concave, dorsal margin convex. Anterior byssal retractors fastened before the umbones. Siphonal prolongations of the posterior part of the mantle are similar like those found in Lithophaga , but with papillae on the rim of the branchial part ( Soot-Ryen 1955: text-figs. 74–76).

Remarks. Anal and branchial part of siphons fused as in Lithophaga , while separated in Botula . The elongate form is similar to Lithophaga spp., which never develop a keel-like structure as in Adula . A concave ventral margin may occur only in L. aristata ( Dillwyn, 1817) and Botula . Adula may be distinguished from Lithophaga by the umbones being distinctly off the anterior end, its lesser height in proportion to its length, and the somewhat inclined posterior half of the shell, the cross-section there being less oval but more diamond-shaped ( Fig. 1 ).

Figures

FIGURE 1. Shell characters of boring mytilid genera Botula, Lithophaga, Adula, Gregariella, and of non-boring “ Notobotula ”. (a) left lateral view, (b) anterior view, (c) posterior view.