PINNA AND THE PEA-CRAB. 263 



been deserted, but during the life of its occupant. 

 The pinna and other mussels, and the cockle, are 

 the favourite dwelling-places of the pea-crab. 

 The species called Pinnotheres veterum, takes 

 up its residence in the shell of the pinna only, 

 a bivalve so large as to measure sometimes 

 three feet in length, and deriving its appellation 

 from the resemblance it was supposed to possess 

 to the pinnce or plumes worn by the Roman 

 soldiers. This habit of the pea-crab was known 

 to the naturalists of classic times, who fancied 

 that the crab discharged the office of intimating 

 to the pinna the moment when, by suddenly 

 closing its shells, it might seize upon some unwary 

 fish that might serve for its food. For this reason 

 this minute member of the crab family was called 

 Pinnophylax, or the pinna's keeper. To this 

 fable the Greek poet Oppian refers in the follow- 

 ing lines : 



" In clouded deeps below the Pinna hides, 

 And through the silent paths obscurely glides ; 

 A stupid wretch, and void of thoughtful care, 

 He forms no bait, nor lays the tempting snare ; 

 But the dull sluggard boasts a Crab his friend, 

 Whose busy eyes the coming prey attend. 

 One room contains them, and the partners dwell 

 Beneath the concave of one sloping shell ; 

 Deep in the watery waste the comrades rove, 

 And mutual interest binds their constant love : 

 That wiser friend the lucky juncture tells 

 When in the circuit of his gaping shells 

 Fish wandering enter ; then the bearded guide 

 Warns the dull mate, and pricks his tender side ; 

 He knows the hint, nor at the treatment grieves, 

 But hugs the advantage, and the pain forgives. 

 S 4 



