MUSSELS SAND PECTENS 43 
room, sending out short spines and thorns for de- 
fence. Sometimes it becomes a giant indeed, with 
thick shells four or five inches long; but more often 
it is considerably smaller. The ligament is inter- 
nal, lodged in a deep, narrow pit; the central mus- 
cle-secar is smooth and very large. Live specimens 
are not common, but dead shells are thrown up all 
along our coast. Figure 22 shows a long and nar- 
row specimen. 
Lima dehiscens, Conr., (Lima orient- 
alis), the File-shell, is shown in Figure 
23. It resembles a Pecten, but the ears 
are small. The animal can swim freely. 
The shell is pure white, delicate, oblique, 
the valves gaping on one side. Seulp- 
turing fine and straight, like the teeth of a file. It 
is sometimes thrown up by storms, and is also 
found attached to seaweed. Some specimens grow 
much larger than the figure. It occurs from Mon- 
terey southward. 
Fig. 23 
