262 MARINE INVERTEBRATES 
annual catch on the Atlantic coast of North America amounts to 
many millions of lobsters, the money value of which is very 
large. 
H. americanus, the common lobster of the Atlantic coast. The 
characteristic feature of the lobster is its enormously developed chele, 
or pincer-claws, which are on the 
first pair of walking-feet. Small 
claws occur on the next two pairs, 
and simple hooks on the remain- 
ing two pairs. The appendages 
on the abdomen are divided (bira- 
mous). In the female they are 
used, excepting the last pair, for 
holding the eggs; in the male 
they are greatly abridged. The 
appendages on the next to last 
segment are divided and broadly 
flattened, forming with the telson 
a powerful swimming-paddle. 
The rostrum is very prominent, 
and has a long, pointed end, 
slightly upturned, and several 
spines. 
The lobster belongs to the 
creeping forms of the order; it 
walks forward by means of the 
ten feet, but swims backward by 
using its caudal fin. It lives in 
deep water on rocky bottoms, 
hiding among stones, etc., but 
frequents sandy shores as well. 
It lives on dead and decaying 
animal matter, and it would seem 
strange that its flesh is so pala- 
table, were it not that we know 
that chemical combinations which 
take place in the assimilation of 
food make one kind as clean, 
when transformed, as another. 
All the crustaceans have a sim- 
Homarus americanus, American lobster; male. lar dietary, being scavengers of 
the sea; yet fishes find them more 
acceptable than other animal food, and fishes capable of capturing larger 
prey subsist largely on the minute entomostracans described elsewhere. 
The lobster is so large that it can easily be dissected, and will serve as a 
type of the structure of Crustacea. In dissecting one can follow the 
descriptions given of the anatomy of Crustacea on page 246, and will be 
interested in observing the beautiful arrangement of the parts and their 
adaptation to the uses they serve. : 
