78 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loe 



are in the collection of the U. S. National Museum. Depths, when 

 specified, from 10 to 30 fms. 



Remarks : The outer lip of the holotype is somewhat broken. Some 

 specimens are entirely grayish white or ashen without any rosy tint 

 but aside from this and the variability of the intercalary threads and 

 the piling up of incremental lines into incipient axial sculpture, there 

 is little variation in the specimens examined. This species is named 

 in honor of Mr. Olaf Avenosook, an Eskimo who served G. E. 

 MacGinitie as boatman during the summer of 1948. 



Margarites frigidus Dall, 1919 



Plate 2, figure 7; Plate 3, figure 7 

 Margarites frigidus Dall, 1919b, vol. 56, p. 357. 



This species was dredged from depths of 120 to 741 feet. Fourteen 

 individuals (mostly from l.G to 2.5 imn. in height, but a few up to 6.5 

 mm.) came from 741 feet; 21 (mostly from 1.7 to 2.3 mm., but up to 

 6.0 mm.) came from 477 feet; 4 (from 1.5 to 2.4 mm.) came from 453 

 feet; and 9 (ranging from 3.0 to 7.0 mm. in height) were found among 

 foliaceous bryozoans at a depth of 120 feet on Sept. 15, 1948. The 

 largest specimen, 7.0 mm. in height, came from 130 feet on Aug. 9, 

 1949. One or two specimens were found in hauls from other depths, 

 but the majority were very small. 



The ovaries of several of the larger specimens of M. frigidus taken 

 from 741 feet were filled with large eggs (larger than those of M. vahli) 

 encased in thick membranes. These large eggs indicate that the 

 larvae of M. frigidus nmst hatch in the crawling stage, and it is even 

 possible that the eggs are retained until they hatch. 



Other material examined: About 17 specimens, including the 

 type, from Bering Strait and the Arctic Ocean. 



Discussion: In some specimens the umbilicus is entirelj" closed and 

 in others it is a mere slit. The young of M. frigidus have a more open 

 umbilicus than larger specimens and hence may be difficult to dis- 

 tinguish from the young of M. vahli of similar size. The similarity is 

 especially marked if they are in alcohol or other fluid, for then the 

 delicate, incised lines on the base near the umbilicus of M. frigidus are 

 often invisible. However, if the shells are allowed to dry, M. vahli 

 remains as glossy as ever and M. frigidus becomes duller, with a silky 

 rather than a glossy surface. 



Distribution: The range of M. frigidus is from approximately 

 long. 134° to 170° W. and lat. 57° to 71° N., or from the Admu-alty 

 Islands (near Juneau), Alaska, to Nunivak Island, Bering Sea, and 

 north and east to Point Barrow. The latter is a new locality. In 



