146 THE GASTROPODA 
with very numerous marginal teeth, arranged like the sticks of a fan. 
Fic. 125, 
Patella vulgata, in its shell, seen from the pedal surface; 7, y, the median antero-posterior 
axis. «a, cephalic tentacle; b, plantar surtace of the foot; c, free edge of the shell; d, the 
branchial efferent vessel carrying aerated blood to the auricle, and here interrupting the circlet 
of gill lamellae; e, margin of the mantle-skirt ; f, gill Jamellae—special pallial outgrowths (uot 
ctenidia) ; g, the branchial efferent vessel ; h, factor of the branchial advehent vessel ; 7, inter- 
spaces between the muscular bundles of the root of the foot. (After Lankester.) 
Oesophagus with a frill, oesophageal glands (Fig. 124, XVI), and a 
stomachal caecum, often coiled in a spiral (Fig. 127, spc). Heart with 
two auricles ; ventricle traversed by the 
rectum (Fig.55) except in the Helicinidae, 
in which there is only a single auricle 
and the rectum only passes through the 
pericardium. An epipodial ridge on each 
side of the foot (Fig. 130, VIII), and 
cephalic expansions between the tentacles 
often present. 
FamMiLty 1. PLEUROTOMARIIDAE. 
Visceral mass and shell spiral; mantle 
and shell with an anterior fissure (Fig. 
54, III) near the median line. ‘Two 
Bathysciadium, ventral aspect, magni- ctenidia ; a horny operculum. Genera— 
fied. ap, cephalic appendage; f, toot; Plewrotomaria, Defrance ; epipodium with- 
RS ese Te bac, pallial’ out tentacles; two bipectinate ctenidia 
(Fig. 127). Five living species from the 
Antilles, Japan, and the Moluccas. The first recent species (P. quoyana, 
Crosse and Fischer) was discovered in 1856; the animal was first 
Fic. 126. 
: 
. 
