The Limpets. Tent Shells 



is olive green. A cap-shaped form, with coarse sculpturing is the 

 extreme of variation in this species. Length, ij inches. 



Habitat. — California. 



The Ghost Limpet (A. spectrum, Rve.) has a ghostly print 

 of a human hand showing under the white callus that lines the 

 shell. Outside, strong rough ridges run from the peak to the 

 crenulated margin. They are whitish, with dots of brown filling 

 in the depressions. Shell heavy. Length, i^ inches. 



Habitat. — Sitka to Lower California. 



The Mask Limpet (A. persona, Eschs.) has its beak bent 

 forward until it is parallel with the base, and almost above the 

 anterior edge of the shell. Behind the apex the curve is rounding. 

 Thus the shell has almost a perfect mask form. Strong rounded 

 ridges, with wide flat spaces between, radiate from apex to margin, 

 crenulating the latter. The colouring varies from olive green 

 to black, with speckles or stripes of white. 



From San Francisco north and south the type diverges, becom- 

 ing more stronglyribbed behind the apex as we go north, and tend- 

 ing to smaller and narrower ribs and more spreading sides as we go 

 south. It is an exceedingly variable species. Length, i inch. 



Habitat. — Sitka to Lower California. 



The Shield Limpet {A. pelta, Eschs.) has an oval, shield- 

 shaped shell, with pointed apex near the centre, and low, coarse ribs 

 radiating from it. A narrow black band follows the edge of the lin- 

 ing, which is oftenest made up of scallops or disconnected square 

 spots. The peak is more elevated than usual in a small form found 

 near Olympia, living on the valves of mussels. The typical colour- 

 ing is gray, striped with black, often tesselated. Length, 2 inches. 



Habitat. — Aleutian Islands to Southern California. 



The White Cap (A. mitra, Eschs.) has a creamy smooth 

 shell, rounded up to a decided peak. The dead shells are often 

 picked up on Pacific beaches, but the mollusk is rarely seen 

 alive. It is scarcely an inch in height, and slightly more than 

 an inch across the almost circular base. 



THE OWL SHELL 



Genus SCURRIA, Gray 



Shell large, oval, depressed, apex far toward front margin, 

 radiating ridges obscured, except near margin, back brownish 



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