MOLLUSCA. 
class Mollusca constitute one of tlie four great divisions of the 
an 'mal kingdom. In its typical figure, “ the mollusc, as represented 
I' 1 F ig. 120, presents the following parts, and is supposed to be 
^laterally symmetrical : h, is the ha?mal parts, in which the heart is 
dilated, commonly called the dorsal part, although the word is 
l,S( d in a different sense in different divisions of the. animal 
j^gdom. In the same manner the opposite region (n) is not 
v rtn ed the ventral, hut the neural part, in philosophical anatomy. 
^ the region in which the great centres of the nervous system 
placed. The termination (a) is the anterior or oval part ; 
le other end (6), the posterior or anal part : between these 
entities the intestines take a straight course. Ihe neural 
^ lr |ace is that upon which the majority of molluscs move, and by 
^ich they are supported, and it is commonly modified to subserve 
* 6Se purposes by the formation of a muscular expansion or disk, 
^Ued the foot. Three regions, in many genera very distinctly 
(1Vl ded f rom one ano ther, may be distinguished in this foot: an 
au terior, the Propodium [p p) ; a middle, the Mesopodium (ms); 
11 a posterior, the Metapodium (m t ). In addition to these, the 
) lp P er part of the foot, or middle portion of the body, may be pro- 
° n § e d into a muscular enlargement on each side, just below the 
