THE GASTROPODA 169 
— 
spire. Genera— Bulla, Linnaeus; British. Haminea, Leach; British 
(Fig. 98). Fantiy 6. Acrratripa®, Pilsbry. Cephalic shield continuous 
with the neck ; twelve to fourteen chitinous stomachal plates ; a posterior 
pallial filament passing through a notch in the shell. Genera—Acera, Om 
Miiller; British (Fig. 147). Cylindrobulla, Fischer. Volvatella, Pease. 
Famity 7. Apnusrrmar, Chenu. Foot very broad ; cephalic shield with 
Fic. 149. 
Hydatina vevillum, as seen crawling. a’, anterior part of the foot ; b, b’, cephalic tentacles ; 
i, shell. (From Lankester, after Adams.) 
four tentacles ; shell external, thin, without prominent spire. Genera— 
Hydatina, Schumacher (Fig. 149). Aplustrum, Schumacher. Mzcromelo, 
Pilsbry. Famity 8. Partnintpar, Adams.. Cephalic shield broad, thick, 
and simple ; shell wholly internal, thin, the spiral much reduced and the 
aperture very large. Genera—Philine, Ascanius (Fig. 58); gizzard with 
three similar calcareous masticatory plates; British. Cryptophthalmus, 
Ehrenberg. Chelinodura, Adams.  Phanerophthalmus, Adams. — Colpo- 
daspis, Sars; British. Colobocephalus, Sars. 
Famity 9. Doripipask, Fischer. Cephalic 
shield ending posteriorly in a median point ; 
mantle well developed ; shell internal, 
largely membranous ; digestive canal with- 
out radula and without masticatory plates. 
Genera — Doridiwm, Meckel. Navarchus, 
Cooper. Famity 10. GaASTROPTERIDAE, 
Fischer. Cephalic shield pointed behind ; 
shell internal, chiefly membranous with a 
calcified nucleus, nautiloid ; parapodia well 
developed, forming fins. Gastropteron, Kosse. 
Famity 11. Rounowniaz, Adams. Cephalic 
shield continuous with the dorsal integu- 
ments of the body; no shell ; ctenidium Mieiiocnevus sable (As dere 
projecting from the mantle cavity; four aspect; B, ventral aspect; C, the 
stomachal plates. Genus—Runcina, Forbes ; Selb. A, foot jana eer oe 
British, Famity 12. LOPHOCERCIDAE, flected on the shell; m, mouth ; 
Adams. Shell globular or ovoid, external ; iy: be eet a ee 
foot elongated, the parapodia separate from 
the ventral surface of the foot ; genital duct diaulic ; visceral commissure 
short. Genera—Lobiger, Krohn ; parapodia divided into two fins on each 
Fic. 150. 
