" SHELL-FISH." IQ5 



by a byssus to the rocks, as is done by the Mussels, Carpet- 

 shells, and others. It is a peculiarity of the Pectens that they 

 have a pair of " ears " to the shell, the edges of which afford a 

 good foundation for the hinge ligament, whilst in lieu of hinge- 

 teeth to keep the valves firmly together when closed by the 

 muscles, the corrugations of the valves extend right to the 



COMMON SCALLOPS. 



margins, and the ridges of the right valve fit into the furrows 

 of the left valve and vice versd. It will be noticed that these 

 ears are not a good pair one is always larger than the other, 

 and the smaller one is popularly supposed to have been 

 broken ; that, however, is a mistake, the Pectens are built 

 that way. The most prominent ear is always the front one, 

 and below that of the right valve there is a notch where the 

 byssal threads issue. In the Common Pecten these ears are 

 much more nearly equal than in the others, whilst in P. Darius 

 there is a great contrast in the size and shape of the two, 

 and in P. tigrinus one is almost absent altogether. 



The Common Pecten is sometimes dredged for, but as a 



