174 



ARTHROPODA 



An important genus, Lunnoria^ is found attacking submerged 

 wood, sometimes honeycombing piles more than half an inch. Piles 

 are accordingly creosoted or infiltrated with paraffin. (Figure 79.) 



The order Decapoda includes our common crabs, shrimps and 

 lobsters. The first three pairs of thoracic appendages are modified 

 as maxillipeds, the thoracic segments are covered by a carapace 

 and there are five pairs of thoracic walking legs. The compound 

 eyes are stalked. 



Fig. 79. Limnoria. (Courtesy of C. A. Kofoid.) 



There are two distinct genera oi crayfishes in America, Cambarus, 

 found east of the Rocky Mountains, and Astacus extending to the 

 Pacific coast. The latter genus includes individuals that grow to 

 a length of 9 inches. The largest crayfish in the world, Astacopsis 

 franklinii, found on the northwest coast of Tasmania, may weigh 

 as much as 9 lbs. 



The American lobster, Homarus americanus, the European lob- 

 ster, H. grammarus, and the Norwegian lobster, Nephrops nor- 

 wegicus, are extremely important as food of fishermen and when 

 served as delicacies inland. The lobster is found along the Atlantic 

 coast, ranging from North Carolina to Labrador. The largest 

 lobster ever taken weighed 34 lbs. and was 23.75 if^ches in length 

 (Herrick). 



