g34 APPENDDt 



Order 3. Oxyuroidea. PinworniS. 



Order 4. Strongyloidea. Hookworms. Ancylostoma, Necatof. 

 Order 5. Filarioidea. Loa, Wuchereria. 

 Order 6. Trichuroidea. Trichinella and whipworms. 

 CLASS 5. GORDIACEA (or NEMATOMORPHA). Hairworms. Reduced digestive 



tract and no nephridia. Two orders. 

 CLASS 6. ACANTHOCEPHALA. Spiny-headed worms. Endoparasitic aschelminths 

 with no mouth or digestive tract. Three orders. 



PHYLUM 8. ENTOPROCTA. Pseudocoelomates with a circle of ciliated tentacles sur- ± 



rounding both mouth and anus. One order in one class. " 



PHYLUM 9. NEMERTEA. Ribbon worms. With a circulatory system but no body cavity. 

 An e%ersible proboscis lies in a special cavity in front of the 

 mouth. Two subclasses and four orders. 



PHYLUM 10. MOLLUSCA. With a ventral foot and dorsal shell. Coelom reduced, circu- i 



latory system with extensive sinuses. I 



CLASS 1. AMPHINEURA. Foot flattened, shell in more than two pieces. | 



Order 1. Polyplacophora. Chitons. Shell a dorsal row of eight plates. 

 Order 2. Aplacophora. Shell reduced to buried spicules, body worm- 

 like. 

 CLASS 2. GASTROPODA. Snails. Foot broad and flat, shell single and usually 

 coiled. 

 Order 1. Prosobranchia. Abalone, Busycon. 

 Order 2. Opisfhobranchia. Pteropods, nudibranchs. 

 Order 3. Pulmonata. Garden snails, slugs. 

 CLASS 3. SCAPHOPODA. Tooth shells. Foot conical, shell tubular. One order. 

 CLASS 4. PELECYPODA. Foot spadelike, shell hinged dorsally with two lateral 

 valves. 

 Order 1. Protobranchiafa. Gills plumose, palps large. 

 Order 2. Filibranchiafa. Marine mussels and scallops. 

 Order 3. Eulamellibranchiata. Clams, oysters, fresh-water mussels. 

 Order 4. Septibranchiata. Gills form horizontal partitions in mantle 

 cavity. 

 CLASS 5. CEPHALOPODA. Foot forms tentacles and siphon. 

 Subclass 1. Ietr-^branchiata. Four gills, chambered external shell, no 

 suckers on tentacles. 

 Order 1. Nautiloidea. The chambered nautilus, 

 t Order 2. Ammonoidea. Ammonites. Partitions in shell wrinkled. 

 Subclass 2. Dibr.\nchl\ta. Two gills, shell internal or absent, arms with 

 suckers, 

 t Order 1. Belemnoidea. Belemnites. Shell straight, slender, heavy. 

 Order 2. Sepioidea. Cuttlefish. 

 Order 3. Teuthoidea. l.oligo: deep-sea squids. 

 Order 4. Octopoda. Octopuses. 



PHYLUM 11. ANNELIDA. Segmented worms with a large coelom and a closed circulatory 

 system. Protostomous. 

 CLASS 1. POLYCHAETA. With parapodia and numerous chaetae. 

 Order 1. Errantia. Nereis, Autolytus, Palolo worm. 

 Order 2. Sedenfaria. Hydroides, lugworm. 

 CLASS 2. ARCHIANNELIDA. Small marine annelids with simplified body. Once 

 thought to be ancestral to other annelids, now believed to have 

 come from the polychaetes. One order. 



