306 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



fiss.; sinu latiore; zona postice fissata, setis tenmoribiis, planatis, pal- 

 lidis, minus confertim obsita. Lon. 50, Lat. 25 nun. 

 Var. Swanii : t. omniuo rufa, sculptura tenuiore. 



Hah. — TJnalaslika, Aleutian Islands (rare and small) to Sitka, and 

 southeastward to Monterey, California; from low Avater to twenty fath- 

 oms, adhering to solid objects, stones, and shells! Two hundred and 

 lifty four specimens examined. 



This species may be recognized by its broad, yellowish, downy girdle, 

 ■nheu fresh, often encroaching far into the sutures ; by the absence of 

 false a[)ices, such as are found in ciUata ; by its color, in which vermillion 

 and verdigris green are beautifully mingled (except in the var. Swanii, 

 which is pure red) ; and by the softness of the flattened and less crowded 

 hairs. The girdle-fissure is not constant, though usual. It is nearly 

 white inside; the sinus is broader and the valves, as a whole, longer in 

 an axial direction, making them less transverse than in ciliata. It is one 

 of tlie most beautiful of all Chitons, when closely examined. 



An examination of the soft parts afforded the following notes on this 

 species : 



The " fringe," or true mantle-edge, is entire, extending around the whole 

 body Avithin the edge of the girdle, and slightly notched at the posterior 

 sinus of the girdle. Veil short in front and broad at the sides, ending 

 behind in two broad, squarish lappets, the edge crenulate throughout. 

 Anus median, distinct. Ovary single, tortuous, overlying the viscera, 

 with no distinct oviduct, so far as could be observed. In texture, the 

 ovary resembles that of Acmcea. If there be an oviduct, it passes from 

 the under side of the sac, one-third of the way forward from the poste- 

 rior end of the ovary. Behind the ovary are two " slime glands" (Midd.), 

 one on each side, opening outward by a plain opening in a fold of the 

 integiunent, one on each side between the branchiae and the anus. They 

 are not present in all Chitons. Schifl' did not find them in G. piceus. 

 Gills about thirty-eight in number on each side, extendiag forward about 

 two-thirds the length of the foot. 



Extra-limital Species. 

 Subgenus Placiphorella Cpr. 



Placiphorella sinuata. 



Mopalia siunaia Cpr. Proc. Acad. Nat. Sci. Philad. 1865, p. 59. 



P. t. lam. sutur. planatis, ab apice antico-externo separatis, sinu an- 

 gustissimo; dent, valde sufifultis. 

 Hal). — Puget Sound and San Francisco Bay, Cal. 



Placiphorella imporcata. 



Mopalia imporcata Caqieutcr, 1. c. p. 59, 18G5. 



P. t. lam. sutur. et apice antico ut in P. sinuata^ sinu paullo minius 

 angusta; dent, parimi suffultis; v. ant. octofissata. 



Hah. — Puget Sound; Santa Barbara Ids., Cal. 



