Periploma kaiserae Valentich-Scott & Coan, new species

Figures 1 J– O

Description. Shell ovate-elongate; both valves inflated, right valve slightly more inflated than left; left valve slightly fitting inside right valve; anterior end broadly rounded; inequilateral, anterior end much longer; posterior end broadly rounded to subtruncate, with broad, shallow radial sulcus that is more prominent in left valve; sculpture of fine commarginally arranged granules; entire posterior end finely pustulose; pallial sinus moderately wide and long, extending past beaks; chondrophore small, rounded, anteroventrally directed; lithodesma robust, narrow, just anterior to chondrophore. Length to 15 mm [SBMNH].

Type material. SBMNH 149599, holotype, 1 paired valves; length, 15 mm; height, 10 mm.

Type locality. Bahía de Jiquilísco, Usulután, El Salvador; 13°11'30"N, 88°28'08"W; 11 m, mud and leaves.

Etymology. Named in honor of Kirstie L. Kaiser of Puerto Vallarta, Mexico, who greatly assisted in our understanding of offshore island mollusks in the Panamic Province.

Distribution. Known only from a single specimen from the type locality.

Comparisons. This species is more equivalve, has a longer posterior end, and is more inflated than P. planiusculum G. B. Sowerby I, 1834 (Figures 1 P–R).

Remarks. While we would prefer not to describe a new species from a single specimen, P. kaiserae is easily separable from all other Panamic and Atlantic species in shape, pallial sinus and chondrophore. We presume it has not been previously been identified, due to its very thin shell, which is easily crushed. The habitat in Bahía de Jiquilísco is possibly estuarine, and thus less likely sampled in marine surveys. We are hopeful that with additional sampling in estuarine habitats the known distribution of the species will be greatly expanded.