ls 
52 Beautiful Shells. 
comes from the Greek Ptero, pronounced tero, 
meaning a wing, and cerus—waxen. Both the 
generic and specific names of the second refer to 
the peculiar conformation of the shell, being derived 
from the Latin, and meaning a straight line or 
beak. 
On Plate III. will be found the Imbricated Pur- 
pura (P. imbricata), Fig. 1, which claims a close 
alliance with the Whelks. The generic name has 
reference to the dye yielded by this, as well as all 
the shells of the genus; the specific name comes from 
the Latin imbree—the gutter-tile ; thus tmbricated, a 
term often used in Natural History, means ridged, 
like the roof of a house, where the tiles are placed 
to overlap each other, so that the rain will run off. 
The Persian Purpura, or, as it is called in Latin, 
Purpura Persica, Fig. 2, is another handsome shell 
of this family group; its name indicates the place 
where it is found. The other species described 
comes from South America, and the P. lapillus 
(the meaning of the specific name has already been 
explained), is common on our shores, being found 
in great abundance on the rocks at low water. 
We read in Scripture of Tyrian purple, and there 
is every reason to suppose that the rich colour was 
obtained from these and other shell-fish. 
