THE PECTENS, OR SCALLOP-SHELLS. 3 



and anotlier specimen (No, 1034) is a ter with considerable celerity, with a 



rattle made from the convex valves of a jerking motion, caused by the rapid 



larger species (/'^^/i?« (Trt/ifr/w/^j-) and for- opening and closing of the two valves, 



merly used as a medicine rattle. These producing a recoil which carries them 



rattles are made by piercing a hole along sideways. The young shells of 



through the valves and stringing them some species dart with great rapidity, a 



upon a willow, or similar twig. single jerk carrying them several yards. 



The animal of the fan-shells is exceed- The writer has frequently watched the 

 ingly beautiful. The mantle, or thin Atlantic species (A /rrrt<//fl;;/i'), and when 

 outer edge, which is the part nearest taken from the water, and as long as life 

 the rim or edge of the valves, conforms continues, the animal will open the valves 

 to the internal fluted structure of the and shut them with a snap, the opera- 

 latter, and presents the appearance of a tion producing a short, sharp, percussive 

 delicately pointed ruffle or frill. This sound. 



mantle is a thin and almost transparent The mechanism by which respiration 



membrane, adorned with a delicate fringe and nutrition are secured is elaborate and 



of slender, thread-like processes or fila- exceedingly interesting. The filaments 



ments, and furnished with glands which of the gill-fringe, when examined under a 



secrete a coloring matter of the same tint powerful microscope, are seen to be cov- 



as the shell; the valves increase in size, ered with numberless minute, hair-like 



in harmony with the growth of the soft processes, endowed with the power of 



parts, by the deposition, around and upon rapid motion. These are called cilia, 



the edges, of membranous matter, from and, when the animal is alive and in situ, 



the fringed edge of the mantle which with the valves gaping, may be seen in 



secretes it. This cover is also adorned constant vibration in the water, gener- 



with a row of conspicuous round black ating, by their mutual action, a system 



eyes {ocelli) around its base. The lungs of currents by which the surface of the 



or gills are between the two folds of the gills is laved, diverting toward the mouth 



mantle, composed of fibres pointing out- animalcules and other small nutritious 



ward, of delicate form, and free at their particles. 



outer edges, so as to float loosely in the The shell of the scallops consists al- 

 water. The mouth is placed between most exclusively, says Dr. W. B. Car- 

 the two inmost gills, where they unite ; penter, of membranous laminae coarsely 

 it is a simple orifice, destitute of teeth, or finely corrugated. It is composed of 

 but with four membranous lips on each two very distinct layers, diff"ering in col- 

 side of the aperture. or — and also in texture and destructi- 



The pectens have also a foot, less de- bility — but having essentially the same 

 veloped than in some others of the bi- • structure. Traces of cellularity are 

 valve mollusks, which resembles a crook- sometimes discoverable on the external 

 ed finger, and is capable of enlargement surface, and one species {P. nobilis) has 

 and contraction, and assists the animal a distinct prismatic cellular layer exter- 

 in moving about on the bottom of the nally. As the idea of the Corinthian 

 sea. Some of them have a sort of beard capital \?, believed to have been suggest- 

 {byssi/s), at least when young, by which ed to Callimachus, the Grecian archi- 

 they attach themselves to rocks, sea- tect, by a plant of the Acanthus growing 

 weeds, and other marine bodies, as do around a basket, it is quite possible that 

 the mussels, which are also bearded; the fluting of the Corinthian column 

 while others of the scallops live without may have been suggested by the inter- 

 attachment, and move through the wa- nal grooving of the pecten shells. 



