The Nautilus. 



Vol. XXIII. APRIL, 1910. No. 11 



NEW SPECIES OF WEST AMEEICAN SHELLS. 



BY WILLIAM IIEALEY DALL. 



Several new shells have turned up lately in material received from 

 the Pacific Coast, of which descriptions follow. 



Olivella (anazora Duel. var. ?) porteri Dall. 



Shell of about the form and size of the east American O.jaspidea, 

 with very variable coloration; whorls about seven, spire acute with 

 a very deep and narrow channeled suture not obscured by callus ; 

 surface of the whorls brilliantly polished, smooth, except for micro- 

 scopic spiral close striation which is present on all, but more uniform 

 on particular individuals ; color pale olive, yellow, or whitish, with 

 sharp angular axial brown lines superposed between the suture and 

 the basal fasciole, sometimes forming a tent-like pattern and some- 

 times reduced to fine, close, more or less cloudy zigzags ; a pale band 

 in front of the suture, usually with vivid brown zigzag pointed for- 

 ward, but sometimes plain, the brown lines when present broader and 

 stronger than elsewhere ; basal fasciole short, with a marginal and 

 an adjacent narrow fold or plait anteriorly, lighter than the body, 

 yellow or rich bluish purple ; aperture narrow, simple, with a deep 

 sutural sinus and a moderate parietal callus when mature. Height 

 of shell 15 ; of aperture 9 ; max. diara. 6 mm. 



From sandbars near the entrance to San Diego Harbor, and at 

 Scammon Lagoon, Lower California, Miss J. M. Cooke. U. S. 

 Nat. Mus. 209677. Named in honor of Captain George Porter who 

 collected largely in the Gulf of California, and is supposed to have 

 lost his life at Tiburon Island while on a collecting expedition. 



