198 BULLETIN 112, UNITED STATES NATIONAL MUSEUM. 
Genus SYMMETROGEPHYRUS (Middendorff, 1848) Chenu, 1859. 
SYMMETROGEPHYRUS PALLASII Middendorff, 1846. 
Bull. Acad. Sci., St. Petersburg, vol. 6, p. 117 ; Sibiriscbe Reise, p. 163, pi. 
13, figs. 1-9. 
Arctic Ocean, Bering and Okhotsk Seas, and eastward to the Shumagin 
Islands, Alaska. 
SYMMETROGEPHYRUS VESTITUS Broderip and Sowerby, 1829. 
Zool. Journ., vol. 4, p. 368 ; Conch. Illustr. Chiton, fig. 128. 
Arctic Ocean and Bering Sea south to Bering, Pribilof, and Hagmeister 
Islands. On the Atlantic south to Gape Cod. 
Order APLACOPHORA. 
Family CHAETODERMATIDAE. 
Genus CHAETODERMA Loven. 
CHAETODERMA ATTENUATUM Heath, 1911. 
Mem. Mus. Comp. Zool., vol. 45, No. 1, p. 55, pi. 4, figs. 3, 10, pi. 25; etc. 
Off Prince of Wales Island, Alaska, .50 to 200 fathoms. 
CHAETODERMA MONTEREYENSE Heath, 1911. 
Mem. Mus. Comp. Zool., vol. 45, No. 1, p. 61, pi. 4, figs. 4, 8, 14, 17 ; pi. 
27; etc. 
Monterey Bay, 39 to- 356 fathoms. 
CHAETODERMA ARGENTEUM Heath, 1911. 
Mem. Mus. Comp. Zool., vol. 45, No. 1, p. 62, pi. 4, fig. 7 ; etc. 
Near Naha Bay, Alaska, in 82 to 113 fathoms. 
CHAETODERMA ERUDITUM Heath, 1911. 
Mem. Mus. Comp. Zool., vol. 45, No. 1, p. 59, pi. 4, figs. 9, 11 ; etc. 
Lynn Canal and Chatham Strait, Alaska, in 282 to 313 fathoms. 
CHAETODERMA CALIFORNICUM Heath, 1911. 
Mem. Mus. Comp. Zool., vol. 45, No. 1, p. 64, pi. 4, fig. 6 ; etc. 
Off North Coronado Island, California, in 618 to 667 fathoms. 
CHAETODERMA ROBUSTUM Heath, 1911. 
Mem. Mus. Comp. Zool., vol. 45, No. 1, p. 68, pi. 4, fig. 5 ; etc. 
South of Alaska Peninsula, in 483 fathoms. 
CHAETODERMA SCABRUM Heath, 1911. 
Mem. Mus. Comp. Zool., vol. 45, No. 1, p. 63, pi. 4, figs. 2, 16 ; etc. 
Monterey Bay, in 795 to 871 fathoms. 
CHAETODERMA NANULUM Heath, 1911. 
Mem. Mus. Comp. Zool., vol. 45, No. 1, p. 66, pi. 4, figs. 1, 12 ; etc. 
Off San Diego, California, in 260 to 284 fathoms. 
Genus LIMIFOSSOR Heath, 1904. * 
LIMIFOSSOR TALPOIDEUS Heath, 1904. 
Zool. Anz., vol. 5, p. 28 ; Mem. Mus. Comp. Zool., vol. 45, No. 1, p. 69, pi. 21, 
figs. 7-13. 
Lynn Canal and Chatham Strait,, Alaska, in 282 to 313 fathoms. 
