基本亜種カキゾメフデガイM. swainsonii swainsoniiは太平洋岸産で,黒色の殻皮を被っている。(Pechar et al. 1980)。
Diagnostic characters:
Height 100 mm, breadth 26 mm. Shell thick, solid, elongate fusiform white with yellowish brownish periostracum. Body whorl large, some 60% of the total height. Spires rather flat with a weak shoulder, and growth lines and very low and slender spiral cords which persistent to the base on the body whorl. Aperture narrow with straight outer lip. Columellar lip with 4─5 folds. Fasciole slightly thickened.
Distribution:
North Carolina to Florida, West Indies and off Suriname.
Remarks:
M. swainsonii swainsonii is a Pacific congener and covered with black periostracum.