gd | James A. Grieg. 
strikingly coarser sculpture. The spiral ribs are, for instance, 
only 3 to 4 in number and of considerable strength, owing to 
which fact the shell acquires the appearance of being triply 
to quadruply carinated. On comparison of Verrill’s illustration 
(Cat. Mar. Moll. 1882 Pl. XL II fig. 8) with ours this diver- 
gence becomes immediately apparent. In order to distinguish 
these two forms I would, therefore, Propose as an appellation 
for the American form, Rissoa americana.‘ 
Of the North American form I have had dr follomaeg 
material for examination: 
”Fish Hawk“, 1880, st. 894, 39° 53' N, 70" 58 307 Mn» 
fms. (668 m) fine sand, 40° F (4, 44° C), 7 specimens. 
* Albatross“, 1883, st. 2110, 35° 12’ 10° N; 74° 57s ee 
516 ims. (944 m) blue mud, 40° F (4.44° C), 3 specimens. 
Michael Sars“, 1910, st. 70, 42°. 59’ N, 51° 15 W/ 11000 
fine sand, 3.7° C, 6 specimens. 
Figs. 1—3. Alvania americana (Friele). 1 and 2 from the ”Michael Sars“ 
stat. 70. 3 from the ”Fish Hawk“ stat. 894. 
Fig. 4. Alvania jan-mayent (Friele) from the ”Voeringen* stat. 225. _ 
Of the typical Alvania jan-mayeni I have had for com- 
parison the material from the Norwegian North Atlantic Ex- 
pedition. 
The material from the coast of New-Enoland shows that 
the carination in the North American form is subject to great 
variations. This is still more evident in specimens from the 
”Michael Sars‘, st. 70. They have three spiral ribs. These 
are on one of the specimens strong and well developed as in 
the specimen figured by Verrill. In the other specimens, how- 
ever, the development of the ribs is more or less weak, they 
may even be quite rudimentary. This variation in the sculp- 
ture, moreover pointed out already at an earlier date by 
