PANDORIDAE 469 



ally compressed. Outer surface whitish (opalescent when worn), commonly 

 with numerous, weak, radial, dark lines of periostracum. Interior glossy and 

 with an opalescent sheen. Ossicle inside, under hinge, is opaque-white. Very 

 similar to our figure of the Atlantic hyalijja. Common in sandy mud bot- 

 toms of many California sloughs and bays down to 40 fathoms. 



Genus Entodesma Philippi 1845 

 Subgenus Agriodesma Dall 1909 



EntodesTfia saxicola Baird Northwest Ugly Clam 



Plate 29m 



Alaska to San Pedro, Cahfornia. 



2 to 5 inches in length. A very peculiar, ugly and misshapen clam found 

 along the shore burrowing into rocks. Generally oblong in shape, with the 

 posterior end flaring and gaping. Covered with a thick, rough, brown peri- 

 ostracum which partially flakes oflF when dry. Interior brownish tan to 

 whitish with a slight opalescence. Hinge \\'ithout teeth, but with a rather 

 large, oblong, whitish ossicle lying under the internally placed ligament. 

 Moderately common from Washington to southwest Alaska. 



Genus Mytilimeria Conrad 1837 



A peculiar, bladder-shaped, very thin shell found embedded in compound 

 ascidians or sea squirts. 



Mytilhjieria Jiuttalli Conrad Nuttall's Bladder Clam 



Plate 29q 



Alaska to Lower California. 



I to 2 inches in length, obliquely oval, inflated, very fragile, opaque 

 with a thin, brownish periostracum. Beaks small and spiral. No teeth in the 

 weak hinge, but a small, calcareous ossicle is present. Color white with 

 underlayers of slightly pearly material. Common under rocks at low tide to 

 10 fathoms, always embedded in compound ascidians or sea squirts. 



Fa7?nly PANDORIDAE 

 Genus Pandora Chemnitz 1795 (Opinion 184) 



Pandora trilineata Say Say's Pandora 



Figure 96b 



Cape Hatteras, N®rth Carolina, to Florida and Texas. 



% to I inch in length, almost half as high; half-moon-shaped in outline, 

 and with a strong, squarish ridge along the hinge margin which extends pos- 

 teriorly into a fairly long rostrum. Valves very flat, the entire shell very 



