VARIETIES OF OYSTERS. 149 







of the newer deposits of Italy and Sicily, and also of the 

 Uddevalla shell-bed. Abroad this species ranges from 

 Scandinavia to the Mediterranean. According to Chieri- 

 ghini, it inhabits the Adriatic ; Weinkauff has included 

 it in his list of Algerian shells, under the 'name of 

 A. pectim-formis, Philippi ; the variety, as well as the 



V 



ordinary form, have been taken by M. Martin in the Gulf 

 of Lyons ; Middendorff has recorded it from Sitka Sound, 

 and Dr. Philip Carpenter from the north-west coast of 

 America. 



It differs from A. ephippium in its more regular outline, 

 thinner texture, coloured streaks, peculiar sculpture, the 

 number and position of its muscular scars, and flat (instead 

 of raised) plug. It is also not so susceptible of outward 

 impressions as that species. An A. patelliformis attached 

 to a scallop, although it sometimes partakes of its com- 

 panion's ribs, has also its own natural ribs, which run 

 their independent course from the beak to the margins. 

 The orifice in young specimens is nearly round. The 

 prominent beak somewhat resembles the apex of a limpet. 

 The plug lies in a hollow which is apparently made in the 

 same way as I have suggested with regard to the other 

 species. Owing probably to the green colour of the liver, 

 the rostral area or nucleus of the shell always appears to 

 have a similar tinge. 







A. patelliformis has not received so many names as 

 A. ephippium, and I can only find fourteen of them. 



The Ostreum Slriatiim of Da Costa (but not that of 

 Lister) appears to be this species. It has been placed by 

 some conchologists in the genus Placunanomia of Broderip; 

 but the distinctive character of that genus lies in having 



