148 



THE GASTROPODA 



Dunker. FAMILY 4. HALIOTIDAE, Fleming. Spire of the visceral mass 

 and shell much reduced ; two bipectinate ctenidia, the right being 



oc 



OJl 



Fio. 128. 



Scissurella euglypta, removed from its shell, ventral aspect, magnified, in-.il. right gill ; !n:s, 

 left gill ; m.vi, visceral mass ; oc, right eye ; op, operculum ; p, foot ; pu, mantle ; t, snout ; te, 

 left cephalic tentacle ; te.ep, epipodial tentacles ; te.pa, pallial tentacle ; te.p.o, post-ocular 

 tentacle. 



the smaller ; no operculum. Genus Haliotis, Linnaeus (Fig. 129). 

 FAMILY 5. VELAINTELLIDAE, Vasseur. An extinct family from the 

 Eocene. Shell elongate, with numerous whorls ; columella and partitions 



Fio. 129. 



Haliotis tuberculata, right-side view, d, foot ; i, tentacular process of the mantle, passing 

 througlrithe shell-foramina. (From Lankester, after Cuvier.) 



between the whorls absent ; internal cavity open from base to summit. 

 Genus, Velainiella, Vasseur. FAMILY 6. FISSURELLIDAE, Risso. Visceral 

 mass and shell conical ; the anterior part of the mantle exhibits a slit 

 or a hole in the median line ; two symmetrical ctenidia ; no operculum. 



