148 THE GASTROPODA 
Dunker. Faminy 4. Hatioripan, Fleming. Spire of the visceral mass 
and shell much reduced; two bipectinate ctenidia, the right being 
Pas 
Fic. 128. 
Scissurella euglypta, removed from its shell, ventral aspect, magnified. br.d, right gill; br.s, 
left cill; m.vi, visceral mass ; oc, right eye ; op, operculum; p, foot; pa, mantle; ¢, snout ; te, 
left cephalic tentacle; te.ep, epipodial tentacles; te.pa, pallial tentacle; te.p.o, post-ocular 
tentacle. 
the smaller; no operculum. Genus—Halvotis, Linnaeus (Fig. 129), 
FamILy 5. VELAINIELLIDAE, Vasseur. An extinct family from the 
Jocene. Shell elongate, with numerous whorls ; columella and partitions 
Fie. 129. 
Haliotis tuberculata, right-side view. d, foot; i, tentacular process of the mantle, passing 
through the shell-foramina, (From Lankester, after Cuvier.) 
between the whorls absent ; internal cavity open from base to summit. 
Genus, Velainiella, Vasseur. Faminy 6. FIssurRELLIDAE, 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. 
