10 WEST AMERICAN SHELLS 
By most naturalists the brachiopods are now 
classed with the worms, or at least with the mol- 
luscoidea, instead of with the mollusks, for in many 
respects they differ from the ordinary clams. In 
the first place their shells consist of upper and 
under valves, instead of right and left as in the 
clam, and the creature firmly attaches itself to 
some object by a pedicle which passes through an 
opening in the beak of one of the shells. On this 
account they have long been known as Lamp-shells, 
since the curved valve resembles the bowl of an 
ancient lamp, the hole through its beak being the 
opening for the wick. 
Internally the creature differs from the clam 
still more than it does externally, for it has no rib- 
bon-like gills, like the oyster, but instead it can 
throw out a pair of long arms, which serve both 
as blood purifiers and food gatherers. ‘hese arms 
being also somewhat suggestive of legs gave rise 
to the old name Brachiopod, meaning arm-foot. In- 
ternally there are various hard supports in some 
of the shells, which seem to serve as brackets on 
which the long arms may rest when not in active use. 
Figure 1 is an enlarged 
picture of the Snake’s-head 
Lamp-shell, Terebratulina 
caput-serpéntis, Linn. (Tere- 
bratula  unguiculus), West 
Coast Shells, p. 214. The first 
name does not mean Lamp- ¥ 
shell, but literally it signifies 
the little-shell-in-which-a-hole- 
has-been-bored. You can see Fig. 1, x 4 (*) 
*By permission, from Bulletin of United States National Museum. 
