Vol. 31, pp. 5-8 February 27, 1918 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON DESCRIPTION OF NEW SPECIES OF SHELLS CHIEFLY FROM MAGDALEN A BAY, LOWER CALIFORNIA. BY W. H. DALL. In the course of a revision of the West American collection in the National Museum the following species appeared to be undescribed : ? Scintilla chloris, new species. Shell of a pale green color, translucent, with more or less evident paler rays, the umbo darker than the rest of the disk; inequilateral, rather compressed, the posterior end wider, longer, rounded ; the anterior end shorter, attenuated; the exterior polished, with slight concentric irregu-larities of growth, and extremely faint, partly obsolete radial striulse; hinge with a long amphidetic ligament in front of which in the left valve is a single noduliform denticle, and behind which is a feebly indicated lateral lamella; the scar of the ligament is long and narrow, there is no evident division into ligament and resilium which might perhaps be visible in a perfectly fresh specimen. The interior of the disk is so pol-ished that the muscular and pallial scars are not distinguishable, but under the microscope a sparse punctation can be made out; the margins are entire. Length of valve, 9.0; length of the part in front of the ver-tical from the umbo, 3.0; height, 6.0; double diameter of the left valve, 2.0 mm. Habitat. — Magdalena Bay, L. Cal., collected by C. R. Orcutt. U. S. Nat. Mus. Cat. No. 218179. Two left valves were obtained. The shell is not absolutely identifiable with Scintilla as defined, but seems nearest to that genus, so until it is possible to describe the characters of both valves it seems best to leave it with that genus. Macron orcutti, new species. Shell of moderate size, solid, flesh colored under a brown villous peri-ostracum, the aperture white, the throat pale purple; nucleus lost, re-maining whorls five, moderately rounded, the suture distinct but not 3— Peoc. Biol. Soc. Wash., Vol. 31, 1918. (5)
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