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MOLLUSCA. 
THE class Mollusca—pulpy animals—forms a grand division which 
naturalists have been pleased to make in the animal kingdom, it 
comes immediately below the Vertebrata and above the Annulosa, 
which again stand above the Ccelenterata, which includes the polyps, 
sea-anemones, hydras, and corals, which last, as we have seen, are 
more highly organised than the Protozoa. 
The Mollusca may be divided into two groups, the Mollusca 
proper and the Molluscoida. The Mollusca proper, as represented 
Fig. 119,—P. C. Mollusca. 
in Fig. 119, present the following parts, and are supposed to be 
bilaterally symmetrical : H, is the heemal parts, in which the heart is 
situated, commonly called the dorsal part, although the word is used 
in a different sense in different divisions of the animal kingdom. In 
the same manner the opposite region (N) is not termed the ventral, 
but the neural region, in philosophical anatomy. It is the region in 
which the great centres of the nervous system are placed. One 
termination (a) is the anterior or oral region; the other end (4), the 
posterior or anal region ; between these extremities the intestines take 
a straight course. The neural surface is that upon which the majority 
of molluscs move, and by which they are supported, and it is com- 
monly modified to subserve these purposes by the formation of a 
