^A. mitra.^ On the Pacific coast there are a number of acmæas. /A. mitra/ is often found dead upon the beaches. It is conical in form and pure creamy-white in color. It looks very much like a clown's pointed cap. ^A. patina.^ This is also very abundant in California. Outside it is dark in color and is often incrusted with mineral deposits. Within there is a dark ring around the edge, then a zone of bluish-white, and a patch of brown just beneath the apex. GENUS ^Lottia^ ^L. gigantea.^ This is the largest of the California limpets. Specimens three inches long have been found. The outer surface of the shell is rough and brownish in color. The apex is near one end. Within it is almost black, shining, lustrous, with a horseshoe-shaped muscle-scar under the apex. The color is bluish and brown. (Plate LXV.) FAMILY ~FISSURELLIDÆ~ This is an extensive family, including several genera and a number of species, commonly known as keyhole-limpets. In the general form of the shell they closely resemble the true limpets, the /Acmæidæ/, except that they have a hole, or rather a slit, in the shell just back of the apex. Often this slit is so long that it has entirely removed the apex of the conical shell. GENUS ^Fissurella^ ^F. alternata^, ^F. barbadensis^. These species occur upon the southern shores of the United States, the latter, however, being confined to [pg358] extreme southern Florida. /F. barbadensis/ has heavy longitudinal ribs and is light green within, with a rosy circle about the apical perforation. (Plate LXV.) GENUS ^Glyphis^ ^G. aspersa.^ One of the numerous species belonging to this family which are found on the west coast of the United States. It is about one and a half inches long, grayish-white, with sharply raised longitudinal ridges, slightly rayed, crossed by revolving ribs, which give to the outer surface a decussated appearance. The apex is forward of the center, and is entirely replaced by a round perforation. The edge is wrinkled, and within smooth and white. GENUS ^Lucapina^ ^L. crenulata.^ The largest of the keyhole-limpets; the shell is often four inches in length, while the animal, with its huge yellowish foot and dark-colored mantle, which is thrown back, almost concealing the shell upon its back, is much larger. The apical perforation is very large. Shell flattened, with radiating, rounded, crowded ribs; brownish-white in color; edge crenulated; within pure white. It is found at Monterey, but live specimens are not very frequently seen near the beach. (Plate LXVI.) FAMILY ~HALIOTIDÆ~ GENUS ^Haliotis^