284 Education through Nature 



3. Entomostracans, variable 

 number of legs 



i. Brine-shrimp, Artemia 

 2o Water-flea, Cyclops 

 3. Shell-flea, Daphnia 



SOME CLASSES, ORDERS, AND GENERA OF MOLLUSKS. 



I. Class Lamellibranchs, 

 bivalved shell 



n 



13 s 

 o & 



, Order Monomya { ^ 



2. Heteromya Sea-mussel, Mytilus 



( i . Fresh-water mussel, Unio 



3. Isomya ! 2. Clam, My a 



[3. Quohog, Venus 



1. Order Pteropods Sea-butterflies, Hyalea 



2. Order Opisthobranchs, f i. Sea-lemon, Doris 



with feathery gills \ 2. Sea-hare, Aplysia 



3. Order Pulmonates, 

 air-breathers 



1. Sand-snail, Helix 



2. Slugs, Limax 



4. Order Prosobranchs, 

 aquatic gasteropods 



3. Pond-snails 



1. Limpet, Patella 



2. Litorina 



3. Paludina 



4. Nassa 



3. Cephalo- 

 poda, large 

 mollusks 

 with dis- 

 tinct head 



, Nautilus 

 ;, Ammonites 



2. Order Dibranchs 



1. Paper-nautilus, Argonauta 



2. Poulpe, Octopus 



3. Squid, Loligo 



. 4. Cuttlefish, ,S^w& 



