PINNA. 305 



and very quick -sightecl_, is tlie constant companion of tlie 

 Pinna marina. They live and lodge together in the shell, 

 which belongs to the latter. When the Pinna has occasion 

 to eat, he opens his valves, and sends out his faithful pur- 

 veyor to procure food. If any foe approaches, the watchful 

 Crab returns with the utmost speed and anxiety to his bhnd 

 protector, who, being thus warned of danger, shuts his 

 valves, and escapes the rage of the enemy ; when, on the 

 contrary, the Crab loads himself with booty, he makes a 

 gentle noise at the opening of the shell, which is closed 

 during his absence, and when admitted the two friends feast 

 together on the fruits of his industry. This curious fact, 

 although well known to the ancients, escaped till lately the 

 observation of the moderns. Aristotle tells us that the Pinna 

 kept a guard to watch for him ; that there grew to the moutli 

 of the Plmia a small parasite, having claws, and serving as 

 a caterer, resembling a crab, and termed the PinnojjJii/lao:. 

 In like manner, Pliny mentions a singular animal called Pin- 

 notheres, which, he says, is liable to injury, and therefore 

 prudently hides himself in the shell of oysters. He also 

 speaks of the Pinna as belonging to a genus of shell-fish, 

 produced in muddy water, and constantly attended by a 

 companion, 



X 



