NO. 1863. M0LLUSK8 OF THE GENUS ALVANIA—BARTSCII. 



351 



ALVANIA COMPACTA Carpenter. 



Plate 31, fig. 7. 

 Rissoa compacta Carpenter, Proc. Acad. Nat. Sci. Phila., 1865, p. 62. 



Shell ovate, light chestnut brown. Nuclear whorls two and one- 

 quarter, well rounded, smooth. Post-nuclear whorls well rounded, 

 slightly shouldered at the summit, marked by poorly developed, 

 slightly protractive, axial ribs, of which 24 occur upon the first and 

 second and 30 upon the penultimate whorl. In addition to these 

 axial ribs the whorls are marked by equal and equally spaced spiral 

 cords, which are almost equal to the axial ribs in strength and of 

 which 6 occur upon the first and 7 upon the second and the penulti- 

 mate turn between the sutures. The first of these spiral cords is at 

 the summit, which it renders feebly crenulate. The spaces inclosed 

 between the axial ribs and spiral cords are rectangular pits, just a 

 trifle longer than broad, their long axes corresponding to the spiral 

 sculpture. In addition to the above sculpture the entire surface of 

 the spire is marked by exceedingly fine, closely spaced spiral stri- 

 ations and axial lines of growth. Suture moderately impressed. 

 Periphery of the last whorl marked by a sulcus as wide as those which 

 separate the spiral cords on the spire. Base strongly rounded, 

 feebly produced anteriorly, marked by nine equal and equally spaced 

 somewhat flattened spiral cords, which are about as wide as the 

 spaces that separate them, and the fine sculpture noted for the spire. 

 Aperture broadly ovate; posterior angle obtuse; outer lip thin, 

 showing the external sculpture within; inner lip strongly curved, 

 slightly reflected over and appressed to the base; parietal wall cov- 

 ered with a tliick callus. 



The specimen described and figured is a perfect individual (Cat. 

 No. 204018, U.S.N.M.) and was collected in Bear Bay, Peril Strait, 

 BaranofT Island, Alaska. It has 4 post-nuclear whorls and measures: 

 Length 3 mm., diameter 1.7 mm. Doctor Carpenter's cotypes, four 

 specimens (Cat. N. 4338, U.N.S.M.), come from Puget Sound, Wash- 

 ington. None of these is as perfect as the specimen described and 



figured. 



Specimens examined. 



Catalogue No. 



Locality. 



Number 

 of speci- 

 mens. 



160992 



206308 



204018 (figured) 



204040 



107442 



213692 



203959 



126650 



211610 



15518 



4338 (cotypes).. 



Port Etches, Alaska 



Virgin Bay, Prince William Sound, Alaska 



Bear Bay, Peril Strait, BaranofE Island, Alaska 



Windfall Harbor, Alaska 



Cumshewa Inlet, Queen Charlotte Island, Alaska (10-15 fathoms) 



Saturnia Island, British Columbia (in crop of Harelda) 



Satumia Island, British Columbia (in duck crop) 



Victoria, Vancouver Island, British Columbia 



Barkley Sound, Vancouver Island, British Columbia 



Neah Bay, Washington 



Puget Sound, Washington 



1 

 3 

 1 

 2 

 3 

 17 

 1 

 9 

 160 

 7 

 i 



