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) 



