)436 NATURAL HIS TOUT. 



FAMILY III. PECTINID^E. 



Genus Pecten.* The shell of the "Scallop" is fan-shaped, or nearly circular, and has the 

 following characters the right valve deep, the left valve flat, usually ornamented with radiating 

 libs ; hinge-line eared ; valves united by a narrow ligament ; hinge cartilage internal ; the mantle 

 quite open, its border double, and finely fringed with a row of round black eyes at its edge. The 

 Scallop ranges from three to forty fathoms. Its body is bright orange or scarlet. The shell is used 

 for " scalloping Oysters." The Pectens are characterised by the brilliant red and yellow colouring 

 of their shells, few groups exceeding them in elegance of form and ornamentation. 



Pecten maximus, commonly known as " Scallops " in the London market, " Queens " at Brighton, 

 and " Frills " on the coasts of Dorset and Devonshire, are now almost as much eaten as Oysters ; but 

 they require to be cooked first. 



An allied species has received the name of "St. James's shell " (Pecten jacobcem}. It was worn by 

 pilgrims to the Holy Land. The fossil Pectens found in the sub-Apennine formation of Italy were 

 supposed by early writers to have been dropped by these devout persons on the road. Parnell says 



of the hermit : 



" He quits his cell ; the pilgrim staff he bore, 

 And fixed the scallop in his hat before." 



The aged Pectens certainly are sedentary in their habits, as is testified by the mass of JBryozoa, 

 Serpulce, Alcyonium, and Balani attached to their upper flat valve. They do not, however, fix 

 themselves, like the Oysters, by the deep valve, but some species are moored by a byssus to stones or 

 the stems of the Laminarice. 



The young Pectens swim freely by rapidly closing and opening their valves. The writer, when 

 dredging with Mr. MacAndrew, off Coruiia, has seen Pecten opercularis, two inches in diameter, 

 swim rapidly out of the dredge as it was being hauled up alongside the boat. 



Genus Ztma.t In this genus the valves are equal and obliquely oval ; the front side is straight 

 ^and gaping, the posterior is rounded and closed ; the umbones of the valves are separated ; the hinge- 

 4ine is eared ; the valves are smooth or radiately ribbed ; the muscular impression is large, lateral 

 double ; the shell always white. 



" The Limas are either free or spin a byssus ; some make an artificial burrow when adult, by 

 spinning together sand or coral fragments and shells; but the habit is not constant." (Forbes.) 

 " L. hians is pale or deep crimson, with an orange mantle. When taken out of its nests it is one of 

 the most beautiful marine animals to look upon. .It swims with great vigour, like the Scallop, by 

 opening and closing its valves, so that it is impelled onwards and upwards in a succession of jumps." 

 (Landsborough. ) 



Twenty species are found living at a depth from one to one hundred and fifty fathoms in Norway, 

 Britain, India, and Australia. 



Genus Spondylus. The Thorny Oyster has an irregular shell, with divergent ribs, terminating 

 in foliaceous spines. It is found attached to foreign bodies by the right valve. The umbones of the 

 shell are wide apart and eared, the lower valve has a triangular area to the hinge, and two curved 

 teeth in each valve ; the animal is like that of Pecten. The Spondyli inhabit coral-reefs, being 

 attached to the branches of the growing coral. Seventy species are known living in the tropics. 



A structure analogous to the chambered shell of the Cephalopod occurs in the Thorny Oyster, or 

 Spondylus. In aged specimens the shell, instead of increasing in size, becomes thicker in its interior 

 by the addition of inner layers of shell, which are distinct from the outer and from each other. The 

 cavities thus formed are found to contain water, which, however, evaporates after the specimens have 

 been placed in a dry situation for a long period ; but the water is again absorbed by immersing the 

 specimens for a sufficient number of hours. This reduction of the inner space appears to be effected 

 in order to counteract the continued increment of the shell (by deposits of new shell-matter along its 

 margin from the border of the mantle) at a greater rate than is required for the accommodation of 

 the soft parts of the animal. 



The tubes of Vermetus and Magilus, and the apices of Triton, Turritella, and Euomphalus becomo 

 either partitioned off or filled up solid in the continued growth of the animal. 



* Latin, pecten, a comb. t Latin, lima, a file. 



