88 WEST AMERICAN SHELLS 
marked with lines of growth. The ligament is in- 
ternal, lodged in a small pit, and the pallial sinus 
is small. Valves rather thick, ineurved at the 
edges, angled at one corner. Southern, only 8mm. 
long. 
Neara pectinata, Cpr., the Dipper-shell, is a 
very small affair, nearly globular, with about 12 
prominent, radiating ribs. The posterior end is 
drawn out into a slender tube, so that each valve 
looks hike a dipper. Southern, 6 mm. long. 
We now come to the Myacide, a small family, but 
containing one of the most important species on 
the whole list, if we think of the mollusks only as 
food for man. Mya arenaria, Linn., the Common 
Mya, or Rhode Island Clam, was known in Europe 
and on the Atlantic Coast long ago, and was highly 
esteemed as an article of food, whether it were 
fried, steamed, or made the basis of a chowder. 
It was unknown in San Francisco Bay until 1874, 
when a few specimens were discovered near Oak- 
land, which were named Mya hemphill, Newe., in 
honor of the veteran collector, Mr. Henry Hemp- 
hill. In a little time, however, its true nature be- 
came known, and conchologists realized that the 
Atlantic Mya had crossed the continent, doubtless 
with seed oysters from Chesapeake Bay, and had 
settled down in the western waters. Unlike the 
aristocratic oyster, which propagates but slowly 
with us, the more plebian clam began to fill the 
mud-flats on both sides of the bay with its bur- 
rows, and even ventured outside the Golden Gate 
and began its march up and down the coast. 
