Conchological Memoranda, No. VII. 



Ai'(U'ST 2-^. 1S71. 



PUKLIMIXABY DESCKIPnOXS OF N"e\V SpECIES OK MabIXE MoL- 

 LUSCA VROM THE WeST CoaST OF NORTH AmEEIOA. 



By lionKKT K. i',. Stkakns. 



Pholas Pacifica : Stearns. 



Shell oblong, beaks tvvo-flfths of length of shell from anterior end ; anterior end of valves 

 triangular, pointed: anterior dorsal edge of valves reflected and folded down on the 

 umbos ; lower anterior margin curved, forming a large elliptic-oval gape ; posterior end of 

 valves squarely rounded; shell dull chalky white, sculptured in concentric lines, which 

 anteriorly are laminated and posteriorly become extinct ; valves radiately ribbed, which 

 also become obsolete at the posterior end ; at the intersection of the radiating and con- 

 centric lines the sculpture is pectinated ; an area below the umbos, nearly or quite desti- 

 tute of sculpture, which varies much in prominence in different specimens ; accessory 

 plate sub-lanceolate and bent down on the beaks, anteriorly prolonged over but not cover- 

 ing the aute-umbonal gape ; interior of valves white, enamelled ; internal rib short, curved 

 and flattened. Largest specimen, two and si.\--tenths inches in length, and one and flve- 

 teuths iu.-hes in height. Habitat— Alam?da. San Francisco Bay. California, where in 

 some places it is common in sandy mud between tide marks. Numerous specimens 

 collectod by Messrs. Harford. Hemphill, Drs. Kellogg and W. P. Gibbons. 



Ptyi'hatractus occidentai.is : Stearati. 



Shell elongated, fusiform, rather slender, whitish, traversed by narrow, revolving, 

 brownish threads and much wider intervening spaces; suture distinct, spire tapering; 

 aperture oblong-oval, about half the length of the shell ; within white, polished ; canal 

 short, nearly straight; columellar obliquely, not strongly plicated; length about three- 

 fourths of an inch. Habitat— near the Island of Attou, at tlie west end of the Aleutian 

 Archipelago. 



Pusus (Chrysodomus .') Haufordii: Uteams. 



Shell solid, elongate, regularly fusiform ; spire elevated, whorls si.x; or seven, moderately 

 convex, slightly flattened (in outline) above, with a groove or channel following the 

 suture; color, chocolate brown; surface marked by numerous narrow revolving costaB, 

 which alternate in prominence on the body whorl, and longitudinally by flnc incremental 

 striie, and on the upper whorls by obtusely rounded ribs of more or less prominence; 

 aperture ovate, about one-half the length of the shell, polished, white and finely ribbed 

 within; (the outer lip in perfect specimens is probably finely crenulated;) canal short, 

 nearly straight. Lon. 2.1 ; Lat. .94 in. Number of Specimens, three ; two mature, dead, 

 one junior, fresh. Habitat— coast of Mendocino County, near Big Spanish Flat, Califor- 

 nia, where it was detected by Mi. Harford. 



