CAP-SHELLS. 214 
FAMILY CALYPTREADA. 
Another group of Limpet-like shells are associ- 
ated under this title, represented poorly in the 
British seas, but numerous and much varied in 
their details in those of the tropics. They are 
commonly more or less circular in outline, rising 
into a cone, the tip of which sometimes is pro- 
duced into a spire, which falls over. In the interior 
of the shell, there is in some of the genera a 
variously shaped shelly plate, which is quite want- 
ing in others. 
The animal has a distinct head furnished with 
tentacles, and eyes placed at their bases; the 
muzzle is not produced into a proboscis. The 
tongue is armed with teeth, arranged in rows of 
seven each, the central one differing in form from 
the others. The gill plume is single, and the foot 
is unfurnished with lateral filaments. 
Some of the genera, at least, sit on and hatch 
their eggs. According to Audouin and Milne 
Edwards, the parent Calyptrea “ disposes them 
under her belly, and preserves them as it were 
imprisoned, between the foot and the foreign body 
to which she adheres, her patelloid shell thus 
serving not only to cover and protect herself, but as 
a shield to her offspring. These eggs are oval 
bodies of a yellow colour, enclosed in membranous 
capsules, which are elliptical, flattened, translucid, 
and filled with an albuminous matter. The num- 
ber of these little capsules varies from six to ten; 
they are connected among themselves by a foot- 
stalk, so as to represent a sort of rosette; each of 
them contains from.eight to ten eggs. It appears 
