5 02 SPONDYLID.E. 



Species of Plicatula. 



australis, Lam. penicillata, Cpr. 



cristata, Lam. plicata, Forsh. 



deltoidea, Dkr. regularis, Phil. 



depressa, Lam. reniforaiis, Lam. 

 lineata, Uecluz. 



Genus PEDUM, Bruguiere. 



Shell thin, smooth, compressed ; beaks unequal, di- 

 verging, slightly eared ; right valve deeply notched for 

 the passage of the byssus. Hinge edentulous ; cartilage 

 internal, in a central cartilage-pit ; ligament partly ex- 

 ternal. Adductor scar double; pallial line simple. 



Ex. P. spondyloideum, Gmelin, pi. 128, fig. 5. Shell, 

 P. spondyloideum, fig. 5, a, 5, b. 



The mantle-margin in Pedum is furnished with nume- 

 rous tentacular filaments, as in Sjpondylus, with small, 

 smooth tubercles between them placed at equal distances ; 

 there is a fissure in the mantle on the right side for the 

 passage of the byssus. The foot is small and vermiform, 

 with a thick, silky byssus at its base. The Pedum, of 

 which one species only is known, from the Eed Sea, the 

 Indian Ocean, and the Mauritius, inhabits coral-reefs, to 

 which it is anchored by a byssus, which passes out of 

 the deep notch in the right valve ; it is often found partially 

 buried in masses of madrepores. 



