212 
ANIMAL CURIOSITIES 
increases in thickness internally, fresh layers of 
shell being formed, each of which is separated 
from the others by a water-filled space. 
The scallop or pecten—the latter term being 
a Latin name meaning a “ comb,” and referring 
to the flat and fan-shaped form of its shell— 
is of a bright red or orange colour. One species, 
found in the Mediterranean, has been given the 
name of “ St. James’s shell ” because its shell 
was worn as a badge by pilgrims to the Holy 
Land. 
Although some of the bivalves possess more 
than the usual complement of eyes, possibly 
the most remarkable of the multiple-eyed 
creatures are the double-eyes, four-eyed fish, 
or anableps of South America. 
They grow to a length of about a foot, have 
very broad heads, and inhabit the waters of the 
mud-flats. Each of their eyes is divided into 
two portions by a dark-coloured transverse 
band, the upper part being adapted for vision 
above the level of the water, and the lower 
part for seeing beneath that element. 
This double form of vision is rendered possible 
by the specialized structure of the lens of the 
eye, the top portion being what is termed 
lenticular—that is to say, in the form of a 
double convex lens—while the lower section is 
spherical. 
