BOOK OF SPECIES. 



carinated ribs ; interstices longitudinally striated, 

 and marbled with brown ; inside white. 1 . . . |. 



w. 37. 17. 



P. LONGicosTA. Convex-depressed, reddish 

 brown, with from twelve to fifteen sub-carinated 

 ribs greatly projecting beyond the margin ; w^hite 

 beneath, and the borders acute; vertex obtuse 

 and white. 2 . . . Ij. 



P. UMBELLA. Large, ovate- depressed, with 

 irregular decussated striae, and narrow longitu- 

 dinal grooves ; margin crenated, white or yellow- 

 ish streaked, and sprinkled with dots of pale 

 vermilion or rose-colour in various ways. Up to 

 3 ... 21. W. 37. 34. 



P. COCHLEAR. Ovate-oblong depressed, lon- 

 gitudinally ribbed and striated, one end con- 



