148 ESSENTIALS OF ZOOLOGY 



Elasmobranchii (e las mo bran' ki I, metal plate and gills). Fish 

 with jaws, cartilaginous skeleton, persistent notochord, and placoid 

 scales. Sharks, Rays, and Chimaeras. 



Pisces (Pis' es, fishes). True fish with bony skeleton, gill respira- 

 tion, with jaws and paired lateral fins. Catfish, Perch, Bass. 



Amphibia (am fib' i a, both lives). Cold-blooded, nonscaled aquatic 

 and terrestrial vertebrates with five-fingered, paired appendages. 

 Most of them breathe by gills in the larval stage and by lungs in 

 the adult. Toads, Frogs, and Salamanders. 



Reptilia (rep til' i a), crawling). Cold-blooded forms which are 

 fundamentally terrestrial, usually possessing a scaly skin and breath- 

 ing by lungs. Turtles, Lizards, Snakes, and Crocodiles. 



Aves (a'vez, birds). Warm-blooded, erect forms possessing feath- 

 ers. The forelimbs have become wings. All birds. 



Mammalia (ma ma' li a, mammary or breast). Warm-blooded ver- 

 tebrates with hair and with mammary glands for suckling the young. 

 Cats, Men, Monkeys, W^hales, Seals, Bats, etc. 



Phylogenetic Advances of Chordata 



(1) Notochord and endoskeleton, (2) pectoral and pelvic girdles 

 with limbs, (3) development of dor sally located nerve cord with 

 anterior brain, (4) development of five senses, (5) pharyngeal gills 

 and lungs for respiration, (6) voice production, (7) specialization and 

 coordination of muscles. 



Protochordata (lower chordates). Until relatively recent years 

 the two subphyla, Hemichorda and Urochorda, were not classified as 

 Chordata ; the former was with Annelida and the latter was inde- 

 pendent. With the exception of the value as biological specimens 

 and the use of amphioxus as food by Chinese, this group is of no 

 economic importance. 



Subphylum Hemichorda 



Dolichoglossus, kowalevskii is the common example studied. It is a 

 wormlike animal which burrows into the mud and sand along the 

 seashore. They range from 6 to 10 inches in length. Others of the 

 genus may be as short as one inch or still others as long as four feet. 

 The three portions of the body are proboscis, a ringlike collar, and 

 a segmented trunk. The proboscis, as well as the collar, is hollow 

 and serves as a water chamber. The cavity of the proboscis is filled 



