22 



MOLLUSCA 



Sub-class OPISTHOBRANCHIA 



Sub-class PULMONATA 



Order MESOGASTROPODA 



( = MONOTOCARDIA, PeCTINIBRANCHIA, - StENOGLOSSA) 



Littorina (periwinkle); Strombus, Natica (necklace- 

 shells); Cv/^raea (cowrie) ; Carinaria; Viviparus 

 ( =Paludina) (river-snail); Aponhais (pelican's foot- 

 shell) ; Crepidula (slipper limpet) ; Charonia 

 ( = Tritoma) (trumpet-shell); Cassis (helmet-shell); 

 Pterotrachea; Bithynia (=Bulimus) 

 Order STENOGLOSSA 



( = Neogastropoda) 

 Buccinum (whelk) ; Busy con ( = Sycotypus) 

 (American whelk) ; Nassa ( —Ilyanassa) (dog- 

 whelk); Murex, Ocenebra (sting-winkles); Terebra, 

 Conus (arrow-tooth shells) 



Order PLEUROCOELA 



( = Tectibranchia) 

 Actaeon (actaeon shell); Aplysia (sea-hare); Bulla 

 (bubble shell) 

 Order PTEROPODA 



Cavolina, Limacina (sea-butterflies) ; Clione 

 Order SACOGLOSSA 

 (=Ascoglossa) 

 Elysia, Limapontia (sea-slugs) 

 Order ACOELA^ 

 Sub-order Notaspidea 



Umbraculum; Pleurobranchus ( = Oscanius) (sea- 

 slug) 

 Sub-order Nudibranchia 

 Onchidoris; Glaucus; Pleurophyllidea; Doris (sea- 

 lemon) ; Eolis (sea-slug) 



Order BASOMMATOPHORA 



Lymnaea ( =Limnaea) (pond snail) ; Planorbis 

 (ram's horn snail); Ancylus {= Ancylastrum) (fresh- 

 water limpet) 

 Order STYLOMMATOPHORA 



Helix (land snail); Testacella (shell-bearing slug); 

 Limax, Arion (land-slugs) 



Class SCAPHOPODA Cadulus, Dentalium, Siphodentalium, Pulsellum 



(tusk-shells) 



Class BIVALVIA 



( = Lamellibranchia, Pelecypoda) 



Order PROTOBRANCHIA 



Nucula (nut-shell); Yoldia; Solenomya 

 Order FILmRANCHIA 

 ( = Anisom yaria) 

 Area (Noah's ark shell) ; /4«ow/a (saddle-oyster); 

 Modiolus (horse-mussel); Mytilus (mussel); Pecten 

 (scallop) 



' SeeTurbellaria, p. 13. 



