BIVALVE SHELLS. 43 



with a perpendicular furrowed line, as in the species of the genus 

 Perna. The first family is again subdi^aded into three sections: 

 t valves equilateral, and ears equal ; ft ears unequal, and having one 

 of them generally ciliated with spires within; ttt valves gibbous on 

 one side. 



Ostrea Icevis — The Smooth Ostrea. Plate II. fig. 2. 

 (Pecten Laevis, Lamarck.) Shell thin, flat, suborbicular, 

 and pellucid, longitudinally and transversely striated; one 

 ear considerably larger than the other; colour various, some- 

 times orange, dark pink, &c. Not uncommon on the coast 

 of Northumberland. The striae on this shell are so minute, 

 that they can seldom be seen with the naked eye. 

 F Longitudinal and transverse striae, h h ears or amides. 



Ostrea opercularis — The Lid Ostrea. Plate VII. fig. 

 J 4. Ears nearly equal; shell with about twenty rounded 

 ribs finely striated longitudinally and transversely ; beauti- 

 fully variegated with red, orange, purple, or brown ; upper 

 valve somewhat convex. Inside pure white. Three inches 

 long. Inhabits the British seas. 



The Ostrefe inhabit the ocean ; some lurk in the sand in large beds, 

 others adhere to rocks, and some to the mangrove trees which overhang 

 the sea on the shores of the West Indies. 



The Edible Oysters of Britain are said to be superior to those of all 

 other countries, and are common on many of our coasts. Indeed, this 

 country has been noted for oysters from the time of Juvenal, who flom-- 

 ished in the beginning of the second century. In satirizing Montanus, 

 an epicure, he says : 



He, whether Circe's rock his oysters bore. 

 Or Lucnne lake, or distant Richborough's shore, 

 Knew at first taste. 

 The luxurious Romans were very fond of oysters, and had their layers 

 or stews for them as we have at the present time. Sergius Grata was 

 the first inventor, as early as the time of L. Crassus the orator. He 

 did not make them for the sake of indulging his appetite, but through 

 avarice, and enjoyed great profits from them. Orata got much credit 

 for his Lucrine oysters, for, says Pliny, the British were not then 

 kno^vn. 



The oyster is a very entertaining object to those who are fond of 

 microscopic investigation. In the clear liquor around the animal, many 

 minute, round, liraig animalcules have been found, whose bodies being 

 conjoined, form spherical figures with tails, not changing their place 

 otherwise than by sinking to the bottom, being heavier than the fluid ; 

 these have been frequently seen separating, and coming togetlier again 



