VARIETIES OF OYSTERS. 151 



several species or varieties. Their general form is very 

 inconstant and often irregular. It is more than probable 

 that when a sufficiently extensive series from each place, 

 and especially in the earlier stages of growth, have been 

 carefully examined and compared, many recent species 

 may become " extinct'' in consequence of a reduction in 

 number, and with great advantage to science. Poli gave 

 the animal the name of Peloris. But that was not an 

 oyster. 



Murice Baiano melior Lucrina peloris, 

 Ostrea Circeiis, Miseno oriuntur echini, 

 Pectinibus patulis jactat se molle Tarentum. 



OSTREA EDTJLIS, Linne. 



O. eduh's, Linn. Syst. Nat., p. 1148, F. and H. 2, 

 p. 307, pi. 54, and (animal) pL i, f. i. 



BODY much compressed, although rather thick, of a 

 pale drab colour, more or less tinged with brown : mantle 

 nearly circular : cirri arranged in two rows, the outer one 

 of which is double but irregular, and the inner one single : 

 mouth furnished with a pair of large and nearly triangular 

 lips on each side. 



SHELL round in its young state, and afterwards spread- 

 ing out in front or at the sides, with frequently a more or 

 less curved outline, usually compressed, rather thick, of a 

 dull appearance outside : sculpture, foliated or scaly ; lower 

 valve sometimes strongly ribbed lengthwise ; the entire 

 surface of the shell when young is microscopically shag- 

 reened ; lines of growth well marked : colour yellowish- 

 brown : margins thin and closely appressed or squeezed 

 together, usually semicircular in front and more or less 

 rounded at the sides : beaks small, divided by the cartilage, 



