TESTACEA. 75 



This animal affixes itself to solid substances by a white or grey 

 silky bijssus. 



The Pecten is one of the most restless of the Testacea. It springs 

 amidst the water, sometimes striking the vessel so violently with the 

 shell as to threaten fracture of the glass. The fishermen affirm that this 

 animal is seen springing through the sea in like manner, which is the 

 quickest mode of shifting its situation. As this is effected by sudden and 

 forcible collapse of the valves, if the observer commit his specimens to a 

 shallow vessel, he will soon find it almost completely emptied of the 

 water. 



Small specimens generally ascend the side of the vessel, where, 

 anchoring themselves, they readily survive ; or, some take the same 

 precaution at the bottom. But, large specimens are of more difficult 

 preservation. 



When quiescent and undisturbed, the scallop opens, displaying its 

 beautiful parts : the thick margin studded with two bright ocelli frills ; 

 and tentacula of surprizing length. The latter extended above an inch 

 from a specimen but half an inch in diameter. The margin is half an 

 inch deep, in a specimen of two inches. T speak of the Pecten in gene- 

 ral, not of the P. opercularis only. 



Plate XVII. 



Figs. 1, 2, 3. Pecten opercularis. 



Pecten obsoletus (P. tigrimis). — Plate XVII., Fig. 4. 



This is one of the smallest species of the genus, as it might be cir- 

 cumscribed by a cu-cle an inch in diameter. The surface of the shell is 

 wholly striated ; faintly towards the hinge, more conspicuously towards 

 the circumference. The left ear is by much the larger. Colour of the 

 upper surface red brown ; of the under surface brownish purple red. 



The margin of the animal is studded with beautiful iridescent oceUi, 

 on both lips, as may be seen by the shell opening on a supply of recent 

 water. Numerous tentacular organs, some extending two or three lines. 



