Shell thin, inflated, subovate, longer than high; color rose red with a tinge of salmoncolor; covered with a thin dehiscent papyraceous epidermis produced on the edges of the elevated sculpture; umbones inflated subceutral with the color deeper than on the rest of the shell; sculpture of tine very numerous radiating grooves with broader Hat interspaces or flattened riblets, crossed by fine concentric, slightly irregular narrow ridges made more prominent by the slightly projecting epidermis; on the posterior sixth of the shell the radiating riblets are coarser and slightly rounded, crossed by rather distant more elevated concentric laminae fringed with epidermis; the posterior area separated from the rest of the surface by a slightly elevated somewhat curved radial lamina which is minutely frilled or puckered in such a way that its edge where unbroken is delicately notched. Posteriorly the shell gapes a little; the anterior margin is evenly rounded, below evenly arched, posteriorly subtruncate and everywhere simple and sharp; the cardinal margin is reflected and elevated before the umbo, more depressed behind it with a delicate ligamentary insertion plate; there are no lateral teeth in either valve; in the right valve the inner edge of the hinge-plate is continued as an elevated line above which the upper posterior margin is produced vertically, making this valve a trifle larger than the other, and more angular at the upper end of the truncation; in the right valve are two slender curved cardinal teeth, the longer notched near its tip, in the left valve a single tooth excavated above. Longitude of shell 29; altitude 25 ; maximum diameter 20mm.

This shell differs from all other Cardiums. recent or fossil (except L. cumingi), in the total absence of lateral teeth. The section Lophocardium of Fischer was based on the prominent radial lamina of L. cumingi but an examination made at the British Museum by the courtesy of Mr. E. A. Smith, at my request, showed that that species partakes of the same hinge characters. For this reason I raised the section to the rank of a subgenus under Dr. Fischer's name.
From L. cumingi which was obtained from the same region, the present species differs in form, in details of sculpture, and in the less elevated radial lamina. It is one of the most beautiful shells of the genus, but so fragile that it is extraordinary that even a single specimen was obtained in a perfect state.

Coast of Lower California. Pacific middle America.