288 ostreadjE. 



seas, and is found fossil in the red and mammaliferous 

 crags.* 



P. danicus, Chemnitz. 



With from four to ten radiating folds ; white, or speckled with 

 white on a ruddy ground : hinder auricle not obsolete, at least 

 equal in length to half the anterior one, when small forming an 

 acute angle. 



Plate LII. fig. 1, 2, 7, 8, 9, 10. 



Pecfen septemradiatus, Midler, Zool. Dan. Prodromus (177C), No. 2992 (fide 

 Loven, p. 31). 

 „ triradiatus, Muller, Prodromus and Zool. Dan. vol. ii. p. 25, pi. GO, f. 1, 

 2 (fide Loven and Chemn.). 

 Pseud- Amusium, Chemn. (not Klein) Conch. Cab. vol. vii. (1784), p. 298, pi. G3, 

 f. G0LG02. 



* We are at a loss to discover what was regarded by Montagu in his Sup- 

 plement (p. 61. — Fleming, Brit. Anim. p. 385. — Ostrea Icevis, Turt. Conch. 

 Diet. p. 131.) as the P. Icevis of Pennant, which latter is thus imperfectly charac- 

 terised : — " Both shells convex, with unequal ribbed ears ; the rest of the shell 

 entirely smooth, very small — Anglesea : " and is probably tigrinus of this work. 

 It appears that the author of the "Testacea Britannica" possessed two specimens, 

 the larger of which, measuring slightly more than half an inch, was taken in 

 Falmouth Harbour, (this was possibly exotic, for the locality is a suspicious one,) 

 the smaller (and this was possibly the fry of P. viaximus, or some other indi- 

 genous species, and not the individual described) from the coast of Devon among 

 Sertularice and Nullipores. He states that the shell was nearly equal in length 

 and breadth, so thin as to be semitransparent, was whitish or of a pale ash-colour, 

 not shagrecned, but quite smooth, except the mere wrinkles of increase, and had 

 one of its auricles of ample magnitude, whilst the other was small and a little 

 striated in a longitudinal direction. However insufficient this language proves 

 for indicating with any certainty what particular species was meant out of the 

 hundred or more known members of the genus, it nevertheless describes features 

 which are not combined in any native shell we are acquainted with. Some 

 naturalists have surmised that it was the similis of Laskey, but that gen- 

 tleman expressly declares (Mem. Wern. Soc. vol. i.) that the reception of a speci- 

 men from Montagu (a third or one of the original types ?) had dispelled his pre- 

 vious conjecture of the specific identity of the two shells: moreover, the very 

 different auricles forbid this hypothesis, — in truth, a worn tigrinus would agree 

 far better with the brief diagnosis. 



