MOPALIIDAE 315 



Family MOPALIIDAE 

 Genus Mopalia Gray 1847 



Mopalia ciliata Sowerby Hairy Mopalia 



Alaska to Monterey, California. 



I to 1% inches in length, oblong, usually colored with splotches of 

 black and emerald-green, although sometimes having cream-orange bands 

 on the sides of the valves. Sometimes grayish green with grayish black or 

 white mottlings. Girdle colored yellowish brown to blackish brown. Valves 

 slightly beaked; lateral area separated from the central area by a prominent, 

 raised row of beads. Central areas with many coarse, wavy, longitudinal 

 riblets, which are sometimes pitted between. Lateral areas coarsely granu- 

 lated or wrinkled. Posterior valve small, with a deep slit on each side and 

 a broad, deep notch at the very posterior end. Girdle fairly wide, generally 

 notched at the posterior end and clothed with curly, strap-like brown hairs 

 between which are much smaller, glassy white hairs or spicules. Interior 

 of valves greenish white. Anterior valve granulated and with 8 to 9 coarse, 

 raised rays of beads. A common intertidal species. The subspecies ivosnes- 

 senski Middendorff (Alaska to Puget Sound) is supposed to be without the 

 tiny white spicules in the girdle. 



Mopalia muscosa Gould Mossy Mopalia 



Alaska to Lower California. 



I to 2 inches in length, oblong to oval. Very similar to M. ciliata, but 

 differing in having a very shallow and small notch at the very posterior 

 end. Color usually a dull-brown, blackish olive or grayish. Interior of 

 valves blue-green, rarely stained with pinkish. Girdle with stiff hairs resem- 

 bling a fringe of moss. The following species have been considered by some 

 workers as varieties of 7miscosa, and perhaps with some justification: lignosa 

 Gould, hindsi Reeve, acuta Carpenter, the latter having also been named 

 plumosa and fissa by Carpenter. A common intertidal species. 



Mopalia lignosa Gould Woody Mopalia 



Alaska to Lower California. 



I to 2^4 inches in length, oblong. Color a grayish green or blackish 

 green, rarely with whitish cream and brown, feathery markings. The sculp- 

 turing on the valves is very delicate and may consist only of numerous small 

 pittings near the center. Concentric growth lines in smoother specimens are 

 quite easily seen. Radial ribs absent on the end valves. Girdle solid or macu- 



