306 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



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

 lid is, minus confertim obsita. Lon. 50, Lat. 25 mm. 

 Yar. Swanii : t. oinnino rufa, sculptura tenuiore. 



Hab. — Unalashka, Aleutian Islands (rare and small) to Sitka, and 

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

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

 fifty-four specimens examined. 



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

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

 false apices, such as are found in ciliata; 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 the 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 within the edge of the girdle, and slightly notched at the posterior 

 sinus of the girdle. Yeil 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 Acmcca. 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' 7 (Midd.), 

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

 integument, one on each side between the branchire and the anus. They 

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

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

 two-thirds the length of the foot. 



Extra-limital Species. 

 Subgenus Placiphorella Cpr. 



Placiphorella sinuata. 



Mopalta sinuata Cpr. Proc. Acad. Nat. Sci. Pliilad. 1865, p. 59. 



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

 gustissimo; dent, valde suffultis. 



Hab. — Puget Sound and San Francisco Bay, Cal. 



Placiphorella imporcata. 



Hopalia imporcata Carpenter, 1. c. p. 59, 18G5. 



P. t. lam. sutur. et apice antico ut in P. sinuata, sinu paullo minus 

 angustaj dent, parum suffultis; v. ant. octofissata. 

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



