204 ANNUL AT A. 



CHAPTER XVII. 

 ANNUL A TA— Continued. 



NEPHROPS. BLATTA. PERIPATUS. EPEIRA. 



I.— NEPHROPS.* 



Phylum Annulata (p. 237). 



Sub-Phylum - - - - Arthropoda (p. 240). 

 Class Crustacea (p. 241). 



The Norway Lobster {Nephrops norvegicus) is a vei 



common kind of lobster found, amongst other places, in tl' 



Ti«v.44. Firth of Forth. It is caught in great numbe 



Habits. • ^1 ^ 1 1 . 1 • • • 



m the trawl and is apparently gregarious in 1 



habits. It is a ground-feeder and is fond of shell-fish, bi 



will eat almost any marine animal of a sufficiently sma 



size. It is rather smaller than the common lobster, an 



is at once distinguished by its pale yellow and red coloi 



and its more angular outline. 



The body is perfectly piano-symmetric and is encased i 

 a hard calcareous exoskeleton. As in the Annelida^ \k 



J. whole body is enveloped in a chitinous cutic 



secreted by the underlying ectoderm (or ep 

 dermis), but this cuticle is greatly thickene 

 over certain areas, and is, in addition, converted into a hai 

 plate by the deposition of calcareous matter in the chitii 

 The hard plates are called sderites^ and the soft cuticul; 

 parts between them which make movements possible ai 

 called the arthrodial membranes. 



We can distinguish the body and the appendages, as i 



many Annelida. In the body the largest sclerite is th 



Extern 1 ^ci^<^p(^<^^' This rests like a saddle on the anteri( 



„ ^ half (or more) of the body. The front end 



FGEit'Ui'es • 



produced into a sharp rostrum., and on eith( 



side it hangs down as a lateral branchial plate. Th 



branchial plate can be broken off, and the gills are the 



exposed in the branchial chamber which is plainly only 



* The following description, except in the case of the gills, will apply equal 

 well for the crayfish {Astacus), the lobster {Ho7narus), or the shrimp {Crangon), ai 

 with very little modification for the crab (Carcinus). 



