146 



THE GASTROPODA 



with very numerous marginal teeth, arranged like the sticks of a fan. 



d 



f 



I'atdla vulgatn, in its shell, seen from the pedal surface ; ., j/, the median antero-posterior 

 axis, a, cephalic tentacle ; b, plantar surface 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 ; /, gill lamellae special pallial outgrowths (not 

 ctenidia) ; g, the branchial efferent vessel ; h, factor of the branchial advehent vessel ; i, 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, sp.c). 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. 



FAMILY 1. PLEUROTOMARIIDAE. 

 Visceral mass and shell spiral ; mantle 

 and shell with an anterior fissure (Fig. 

 54, III) near the median line. Two 

 ctenidia ; a horny operculum. Genera 

 Pleurotomaria, Defrance ; epipodium with- 

 . 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 



FIG. 126. 



Bathysciadium, ventral aspect, magni- 

 fied, ap, cephalic appendage ; /, foot ; 



