NO. 1264. ILL USTRA TIONS OF A M ERICA N i^ HELLS— DA LL. 551 
This singular shell is bluish white with an olivaceous brown peri- 
ostracum, and is usuall}' more or less eroded. In the adult there seems 
to be a patch of darker color on the body just outside the callus. Its 
resemblance to a fresh-water shell is obvious, but pending an ana- 
tomical examination it is provisionallj^ referred to the vicinity of 
Trichotropis. 
LITORINA ALEUTICA Dall. 
Plate XXXIX, figs. 4, 6. 
Litorinn dlmtira Dall, Proc. Cal. Acad. 8ei., IV, 1872, p. 271, pi. i, figs. 3, ?>a. 
Gull Rocks in Akutan Pass, and on wave-worn rocks at Kazan Bay, 
Atka Island, Aleutians, Dall. U.S.N.M., 130623. 
The shells are mostly yellow brown, sometimes with lighter bands, 
the throat dark, and the broad pillar white, with a minute umbilical 
perforation. 
LITORINA ATKANA, new species. 
Plate XXXIX, fig. 11. 
Western Aleutians, from Atka Island westward. Figured specimen 
from shore of Little Kyska Island, Kyska Harbor. U. S. N. M. , 108986, 
108987. 
Typical form of shell large, solid, nearh^ smooth, the whorls flat- 
tened next the suture, a few obsolete striations on the base, the gen- 
eral form as figured, the outer lip thin, the pillar broad and white. 
Alt. 20.0, lat. 17.0 mm. 
The most abundant form is of a dark chestnut brown throughout, 
except on the pillar. The variety figured has white bands at the 
suture, periphery, and umbilical region. These bands do not vary in 
position. 
A third mutation, which involves both the preceding color forms at 
times, has the spiral sculpture stronger and more extended over the 
surface, though it never reaches the prominence sometimes attained 
in Z. .'iitl'ana Philippi, wiiich is a much smaller shell without the 
])road white Y)illar. The periostracum, usually not very conspicuous, 
is .sometimes of a light yellow brown and dense enough to obscure the 
underlying white bands. 
I have recognized and distributed this species under the above name 
for some years, but I believe, by some inadvertence, it has never been 
formally described. 
AMAUROPSIS PURPUREA Dall. 
Plate XXXVIII, fig. 9. 
Amauropsis purpurea Dall, Am. Journ. Conch., VII, Pt. 2, 1871, p. 124, pi. xv, 
fig. 16. 
St. Michael, Norton Sound, Alaska, and northward to Point Barrow. 
U.S.N.M., 108988. 
