DIVISIONS OF THE I'OOT. 
1 ;» I 
lively indicate its anterior, middle, and posterior regions, yet in onr 
native species, with the exception of Acicuhi, which, according to 
Dr. (fray, has a transversely divided sole like TruncateUa, these parts 
are so intimately blended together that we are only able to dis- 
tinguish the metapodinm owing to its being indicated by the oper- 
cnlum on its ni)per surface. 
'rhongh not divided transversely, the sole may have well marked 
longitudinal divisions, and this feature is carried to the greatest ex- 
tent in Ci/clostoiixc elegants, in which 
species the foot is medially cleft 
and separated along its whole 
length, each part being advanced 
alternately during locomotion. In 
V(tlv(tf(( pisciiialiti and D. criatxtd 
this cleavage is confined to the 
prolonged anterior part of the foot, where the divided parts become 
widely separated and divergent, simnlating a pair of jiodial tentacles. 
In onr native species of Vlviparx, 
although the anterior portion of the foot 
is similarly prolonged beyond the muzzle, 
it is not medially cleft, so that the crea- 
ture is said to be prevented from feeding 
except when at rest. 
In Lima,)’, A)-io)), etc., the sole is more or less distinctly 
longitudinally tripartite, the side areas being nsnally more darkly and 
distinctly pigmented than the locomotory mid area, owing to the 
thickening of the epithelial and snb-epithelial mnscnlature which 
Fir,. 3Sl . — Cyclostoma elegans, showing 
the longiiutlinally cleft foot, with the right 
segment in use, the left being contracted and 
raised, X 2 (after Simroth). 
Fig. 382. — I’alvaia J>lscifiallsy 
showing the cleft and divergent 
anterior ends of the foot, X 2. 
Fig. 383. — Sole of Lhna.v cine>ro-uiy:e>% showing the trifasciate foot and the muscular waves of 
the mid area, vi.sible during movement (after Simroth). 
prevents its free pigmentation, d'he side and mid areas in Llma.r, 
though not in Ai'hin, are also separated by more or less distinct longi- 
tudinal furrows, which, though often imperceptible during life, become 
visible after the immersion of the animal in boiling water or alcohol ; 
but in the testaceous Enthyneures the entire sole is more or less 
