CLASSIFICATION. xi 



These sometimes resemble worms found in the other 



classes or orders, while differing from them as to their 



locality. They have been arranged into the following 



sub-orders : 



(1). Nematoidea or Nematoids, Round Worms, Thread Worms, 



Pin Worms, Guinea Worms. 



(2). Acanthocephala, (Spine-headed,) Hooked Worms. 

 (3). Trematoda, (from Gr. trema, hole, having Sucker-like 



openings,) Fluke Worms, &c. 

 (4). Cestoidea, (Gr. Kestos, girdle,) Tape Worms. 

 (5). Cystica, (Gr. Kustis, a bladder,) Hytatids or Bladder- 

 like Worms. 



MOLLUSKS. Two GRAND DIVISIONS: 



CepHALATA (with heads) or UNIVALVES. 

 ACEPHALA (without heads) or BIVALVES. 

 I. CEPHALATA : Three classes or Sub-divisions, viz. 



(1). CPO DS ,J SSh'ehead. f^wo sections. 



Dibranchiata, (Two branchiae,) Cuttle-fish. 

 Tetrabranchiata, (Four branchiae,) Nautilus, Ammonites, &c. 



( Wing-footed, i. e., ) 

 (2). PTEROPODS, -j wing-like arms > Three families, 



( for swimming. ) 

 Hyalaida, Hyalaea, Cleodora. 

 Limacinidce, Limacina, Spiralis. 

 Clionidce, Clio. 



(3). 



(1). Pulmobranchia (Lung-like Gills). (Four families.) 



Limacidce, (from Limax t ) Slugs. 



HelicidcE, (from Helix,) Snails. 



Auriculida, (from Auricula*} Ear-shaped Shells. 



Limnaeida, ( " Limncea, Aquatic-Snails. 

 (2). Pectinibranchia, (Comb-like gills.) (Nine families.) 



Trochidce, (from Trochus,) Trochi. 



Turbinidee, (from Turbo,) Turbines, Periwinkles. 



MuricidcB, ( " Murex,) Murices. 



Strombidce, ( " Strombus>) Conch-Shells. 



Succinida, ( " Buccinum,} Harp-Shells, Whelkfl. 



Cyprceidce, ( " Cyprcea,) Cowries. 



Conida, (from Genus,) Cones. 



Volutidee, (from Valuta,) Volutes, Olives, Mitres. 



Capuloidea, (from Capula,) Cup-shaped Shells. 



Tubulibranchia, (Tubular-gills,) Yermetus, Siliquaria. 

 Scutibranchia or j Gills shielded, by ) ,. .. 

 Mpidobranchia,( the Shell. ' f UaUotls - 



T GiUs circular, i. e., ) G ,. 

 Cyclobranchia, < around the body of XT- * 



( the animal. ) ***&* 



