176 OYSTERS, AND ALL ABOUT THEM. 



ground. Var. i, Loch Fyne and Shetland (Barlee). Var. 

 2, Hebrides and Shetland. This species is fossil in the 

 Clyde basin, and in other glacial deposits in Scotland as 

 well as Norway. It ranges from Finmark to the ^Egean, 

 but it appears not to be so common in the south as in the 

 north. The variety Dumasii occurs in the upper miocene 

 strata near Antibes. 



P. scptemradiatns was added to the British fauna by the 

 late Captain Brown, in 1835. It is remarkable that such a 

 handsome and by no means small shell should have pre- 

 viously escaped the notice of Laskey, Fleming, Macgilliv- 



ray, and others of our northern conchologists 



The shell is extremely variable in respect of shape and the 

 number of ribs, as well as of the proportionate size of the 



ears In young shells the surface is regularly 



cancellated. The fry is glossy, and has very prominent 

 beaks ; its sculpture consists of numerous microscopical 

 longitudinal striae on the upper valve, and equally minute 

 transverse striae on b'oth valves. A dozen names have 

 been given by different conchologists to this species. 



5. P. TIGRINUS, Miiller. 



P. Tigerinus, Mull. Zool. Dan. Prodr., p. 248, No. 2993. 

 P. tigrinus, F. and H. 2, p. 285, pi. 51, f. 8-11. 



BODY bright red or occasionally creamy-white : mantle 

 edged with white and mottled with dusky or brown rays : 

 cirri short: ocelli 10, brown with a golden centre: foot 

 white and very flexible : byssus transparent. 



SHELL of the same shape as the last two species, but 

 rather narrower at the back, moderately solid, and some- 



