MARINE MOLLUSKS — MACGINITIE 77 



are all types of combinations of characters and all transitional forms 

 of sculpture. 



Distribution: The variety grandis and forma multilirata are cir- 

 cumpolar. They have been reported from Greenland to the Gulf of 

 St. Lawrence, and from the European Arctic. They have not been 

 reported previously from Arctic Alaska. 



Margarites avenosooki, new species 



Plate 1, figure 8; Plate 3, figures 8, 9 



Shell medium sized, somewhat depressed, with 5K rapidly expanding 

 whorls, including about 1% nuclear whorls. External surface of shell 

 a rosy, grayish white, becoming ashy on the spire and within the um- 

 bilicus. Interior of aperture pearly, with brilliant greenish and pink- 

 ish lines of light, the green bands in shallow grooves corresponding to 

 the spiral cords and threads on the external surface and the pinkish 

 bands to the interspaces. Widely umbilicate whorls visible within to 

 the nucleus. Sculpture of about 8 primary spiral cords on last whorl, 

 with from 1 to 2 secondary threads between the cords near the suture 

 but only one between those near the base; about 7 cords on the penulti- 

 mate whorl, with secondary threads between most of them; about 

 5 cords on the antepenultimate whorl, with no secondary threads be- 

 tween them; about 7 equally spaced steplike cords on the slightly 

 convex ascending base; 3 smaller cords on the descending slope of the 

 base at the beginning of the umbilicus; remainder of the funnellike 

 umbilicus devoid of cords; 5 cords visible on the body whorl between 

 the inner and outer lip of the aperture. Spiral cords crossed by silky 

 incremental lines, resulting in an uneven wavy appearance and, in 

 some places, especially on those cords nearest the sutures, in a slight 

 beaded effect. Aperture large, subquadrately oblique. Lip thin 

 and crenated by the spiral cords. Operculum thin, multispiral, straw- 

 colored. 



Dimensions: Holotype: height. 8.9 mm.; diameter, n.7 mm.; angle 

 of spire, 96°. 



Type locality: About 4 miles off Point Barrow base, Alaska. 

 Depth, 217 feet. Bottom: stones, large perforated rocks. Collected 

 by G. E. MacGinitie, Sept. 6, 1949. 



Repositories: Holot^'pe, U. S. National Museum, No. 606,374; 

 paratype. No. 606,375 (diameter, 2.8 mm., from 341 feet). One 

 paratype (height, 9.2 mm.; cUameter, 11.3 mm., from 420 feet), 

 Stanford Univ. Paleo., No. 8331. 



Other localities: Bering Sea (1 dead), Bermg Strait (1 live, 2 

 dead), north of Bering Strait (1 live), collected by U. S. S. Corvnn; 

 Plover Bay (2 live), St. Lawrence Bay (1 live). All these specimens 



