FOOT FRINGE AND PODIAL LOBES. 
193 
mucous cells. The super-families, Aulacopoda and Holopoda, are 
based upon the presence or absence respectively of the pedal grooves, 
which, when present, are ventrally circumscribed by the Foot Fringe, 
a feature distinctly present in some forms and constituting the lateral 
border of the foot. In Avion it is often very brightly and vividly 
coloured, and variegated at regular intervals by numerous dusky and 
black, alternately placed, vertical lineoles, which in strongly coloured 
individuals may be continued across the side areas of the sole. As 
the tail is approached these lineoles become placed nearer together 
and more obliquely directed. 
The foot, in some groups, gives off various lobes or processes, 
which when arising from the Epipodium, a thickened ridge along 
M the upper margin of the sole, ai'e known 
as Epipodia; the Operculigerons lobe of 
the Streptoneures, which secretes the 
operculum, is a dependence of the hinder 
portion of this e])ipodial ridge, while the 
Fig. 378.— Prosoma of vivipara. Ceplialic lobes of Vivipdva are a develop- 
vivipara $ (after Moquin-Tandon), 
to show the epipodial Cephalic lobes, meiit of the anterior part, such processes 
being distinguished from cephalic tentacles by receiving their innerva- 
tion from the pedal or pleural and not from the cerebral ganglia. 
Analogous processes, termed Parapodia, may, however, originate 
along the basal edge of the sole ; such outgrowths, though highly 
developed in many Opisthobranchs, are not noticeably present in our 
Fig. 379. 
Fig. 380. 
Diagrammatic sections through the body of a Streptoneurous and of a Tectibranchiate Gastropod, 
showing the relative positions of the Epipodial and Parapodial lobes (after Lang). 
Fig. 379. — A Streptoneure ; f. foot, with epipodial lobes ; sh. shell; v.s. visceral or body cavity. 
Fig. 380. — ATectibranch ; f. foot, with parapodial lobes ; sh. shell ; v.s. visceral sac with ctenidium. 
land and freshwater species, although the spreading sides of the foot 
of Helix pomatia may be regarded as incipient parapodia. 
In certain extra-British species, the primitively sole-shaiied foot 
has, by adaptation to special modes of life, lost its original form and 
by transverse constrictions, become formed into three regions, termed 
the Propodium, the Mesopodium, and the Metapodinm, which respec- 
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