440 PATELLID^. 



the membranous sac, when it throws off the empty fihns 

 from its foot." 



This Limpet is universally distributed around our coasts, 

 adhering to shells and stones in various depths of water 

 from the laminarian zone to as deep as twenty or 

 thirty fathoms, most plentiful in from five to twelve 

 fathoms, and occasionally, especially in the Hebrides, 

 where it grows larger than in most places, occurring 

 between tide-marks. It inhabits the Scandinavian and 

 Celtic seas generally, and is found fossil in the red crag 

 and northern drift. 



PILIDIUM, Forbes and Hanlev. 



Shell ovate, conical, with an eccentric anteal apex ; 

 surface with radiating strise ; interior with a crescentic 

 muscular impression, inteiTupted in the region of the 

 animal's head. 



Animal with two subulate tentacles unprovided with 

 eyes; mantle-margin simple; branchial plume cervical; 

 foot large, ovate, with plain sides ; lingual ribband com- 

 posed of a single series of squares, on each of which a 

 single trilobed tooth is borne, flanked on each side by two 

 distinct accessorials. 



The eyeless head, even-edged mantle, and peculiarly 

 constructed tongue of the Patella fulva of the Zoologia 

 Danica forbid our associating it, as has been hitherto done 

 by modern writers, with Acmeea, and demand for it the 

 establishment of a peculiar genus. The shell so closely 

 resembles that of Acniaa, that from it alone the important 

 differences presented by the animal could not be predicted. 

 The only recorded living British species is found fossil in 

 beds of coralline crag age. 



