478 



P. with a pellucid, thin, yellowifli, horn-coloured 

 fhell, of an oval fliape, rounded at the top, with an ob- 

 fcure apex at one end; and beautifully rayed with dot- 

 ted lines of azure : thefe lines vary in number, ufually 

 from three to feven, that are mofl; confpicuous, running 

 from behind the beak to the margin : but the fides in 

 fome are radiated in an obfcure manner. 



This is the defcription of the young fhells, and fuch 

 as have generally been confidered as the P. pellucida. 



Old (hells arefub-pellucid, and mod frequently dufliy- 

 brown ; fome are conic, others quite flat with the vertex 

 nearly central, or a little to one end, radiated with blue 

 in the fame manner as the young, but the colour is lefs 

 brilliant, and frequently very obfcure : thefe bluerays^ 

 in fome, rife into fine elevated ftris all round the fliell, 

 terminating at the apex ; befides which it has fome cir- 

 cular wrinkles: aperture oval, margin plain, rather 

 inclining upwards at each end. Infide gloffy, of a 

 changeable opalacious colour, frequently of a blueifh cafl. 

 Length near an inch ; breadth not quite three-quarters. 



Nothing can be more different in appearance, as to 

 fliape, than this fpecies is in its infant and adult flates ; 

 and were it not for the regular gradations^ would pro- 

 bably have continued to be formed into two or three 

 fpecies ; as Mr. Pennant has done with rcfpetl to his 

 P, Icevis and intorta. He is however not fingular in this, 



for 



