3 8 o 
MOLLUSCS. 
EGG - CAPSULES OF 
Purpura lapillus. 
Like the murices, these molluscs are devourers of Bivalves. The annexed illustration 
represents the egg-capsules of the common British P. lapillus. The animal and 
shell of Acanthina are similar to those of Purpura, but the outer lip of the aperture 
is furnished at the anterior end with a more or less prolonged conical tooth or 
prong. Rapana, Concholepas, and Sistrum are other nearly 
allied forms. The members of the family Coralliophilidce 
resemble the purpuras, but are characterised by the want of a 
radula, and their singular mode of life, dwelling either in or upon 
corals. Rhizochilus in early life is like the young of Purpura, 
but subsequently it attaches itself to barked corals ( Antipathes ), 
living a prisoner’s life, immured within its own shell. It pro¬ 
longs the lips of the shell around the stems of the coral, completely closing the 
aperture, with the exception of the siphonal end, which it extends into a distinct 
tube, serving to carry both water to the gill and food to the mouth. What the 
nature of its nourishment may be—possibly derived from the Antipathes itself— 
and what may be the reason of this self¬ 
immurement, are problems to be solved. 
Coralliophila niadreporarum attaches 
itself to corals; other species live a more 
active life, crawling over the surface of 
the coral. Several are tinted with lilac, 
and have purple apertures; others, however, 
are entirely white. Leptoconchus and 
Magilus are both dwellers in coral. The 
former lives in crypts excavated in brain- 
stone corals, and resembles, as regards the 
shell, the young state of the latter. 
Magilus affects coral-reefs, and is remark¬ 
able for the great alteration which takes place in the course of its career. At 
first it assumes the form of an ordinary spiral shell, and takes up its abode 
within the crevices of growing coral. The coral slowly advances around the shell, 
and would soon enclose it, if the mollusc were not provided with some means of 
defeating this. The creature prolongs the lips of its aperture into a long, but 
mostly crooked tube, so as to keep pace with the growth of the coral, and keep 
the tube open for the free ingress of the water. As the tube increases it becomes 
too long for the animal; consequently the mollusc fills up the spiral portion, and 
as much of the tube as is not required. These shells are found in the Red Sea, 
and the Indian and Pacific Oceans. 
Rhizochilus antipathum. a, Young ; b, Adult. 
SECTION" TiENIOGLOSSA, 
The majority of the molluscs included in this section of Pectinibranchs are 
marine forms; although a few families are found in fresh water, while others are 
terrestrial and air-breathers. Typically, the radula has seven rows of teeth, one 
central, and three laterals on each side; but there are a few families in which this 
armature is modified. Sometimes there is only a single lateral on each side ; but, 
