276 LIFE BY THE SEASHORE. 



The common scallop is not the only edible species of 

 Pecten^ for the much larger P. maximus, often called a 

 clam, is not infrequently seen exposed for sale. It is a 

 very handsome species, reaching a size of six by five inches, 

 and often of a pale colour beautifully mottled with pink. 

 The valves are very unequal, the lower being deeply convex 

 and the upper almost flat, except for a slight concavity near 

 the beak ; it is always much darker in tint than the lower 

 valve. The convex lower valve bears fourteen to sixteen 

 broad, rounded ribs, wider than the spaces between them. 

 In the upper valve the relation of ribs and spaces is reversed, 

 so that the two valves lock closely together, a condition 

 which may be noticed in many Bivalves. The ears are 

 nearly equal, but are concave in the upper valve and convex 

 in the lower. The surface of the shell is quite without the 

 scales of the preceding species, but is marked by distinct 

 radiating striae, which with the broad ribs are very character- 

 istic of the species. Separate valves of this species are not 

 uncommon on the shore, but I have never found the entire 

 animal, either living or dead. Specimens for dissection may 

 be obtained at times from the fishermen. The shells are 

 sometimes used by cooks, and are very commonly sold in 

 fishmongers' shops at a penny apiece, but unfortunately it 

 is usually only the convex lower valves which can be 

 obtained in this way. 



We shall mention one other species only, one which is 

 interesting because, like the oyster, it is fixed when adult, 

 and, as in the oyster, the shell is often curiously distorted. 

 This is P. pusio, odd valves of which may be often found on 

 the shore. The animal is attached by the lower valve, 

 which is usually white, without sculpture, and often of very 

 irregular shape. The upper valve has its surface covered 

 with very numerous (40-80) prickly ribs, often alternately 

 large and small. In the young the ears are unequal in 

 size, and in the adult they become very irregular. 



The next genus is the very beautiful one of Lima, of 

 which we shall consider one species only the delicately 

 tinted L, hians. Strictly speaking it is beyond our range, 

 but is such an interesting and beautiful species, and so 

 common in the Clyde, that we must make an exception in 

 its favour. In it the shell is snowy white, and the mantle a 



