UNSEGMENTED SCHIZOCOELS 



219 



Figure 13.7 Class Gastropoda, univalve types: A, Halioiis shell from above, aboione, marine; B, 

 Megaihura shell from above, keyhole limpet, marine; C, Acmoeo shell from the side and below, limpet, 

 marine; D, Caecum shell, pouch snail or shell, marine; E, Aletes shell, tube snail or worm shell, marine; 

 F, Crepidula shell from below and to the side, slipper shell, marine; G, Crucibulum shell from below 

 and to the side, cup-ond-soucer shell, marine; H, Cyproeo shell from above and below, cowry, marine; 

 I, Triopha, a sea slug; J, Umax, a land slug; K, Helix, a land snail; L, Olivella shell, a marine snail, also 

 called olive shell; M, Aplysia, o sea hare. 



