SPONDYLUS. 



387 



naturalists even assert that, when raised to the surface, the Pecten 

 half opens its shell in such a manner that the upper valve serves the 

 purpose of a sail. 



The Pectens, of which a 

 hundred and seventy-six 

 species are described, are in- 

 habitants of every known sea. 

 Twenty species belong to 

 Europe, among which we 

 may mention P. opercularis, 

 represented in Fig. 177; 

 P. gldber, and P. nivea. 

 Fig. 178 represents the 

 White-mantled Pecten (P. 

 plica, Linn.) of the Indian 

 Ocean, and Fig. 179, the 

 Concentric Pecten (P. Japo- 

 nica) of the Japan seas. 



Among the Ostreadae the shells of Spondylus are distinguished for 

 their variety of form and the brilliant colours with which they are 



Fig. 177. Pecten opercularis (Linnseus). 



Fig. 178. Pecten plica (Linna;us). 



Fig. 179. Pecten Japonica (Gmellin). 



decorated. This makes them much sought after by amateur collectors, 

 and procures for them a high price. The shell of Spondylus is solid 

 and thick, with unequal adherent valves, nearly always bristling with 

 spines, forming a very peculiar kind of ornamentation to the valves ; 

 the hinges have two very strong teeth. The animals which inhabit 

 this shell resemble the oyster in many respects, but they still more 



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