434 General Biology 



Subphylum UROCHORDATA or TUNICATA ( ). 



Sac-like marine animals with a cuticular covering known as a tunic or 

 test. This group possesses a notochord only in the caudal region. 

 Example, tunicates. 



Subphylum HEMICHORDATA ( ). Worm- 



like chordates of doubtful systematic position. There is a projection 

 from the mid-dorsal region of the alimentary canal similar to a noto- 

 chord. These animals possess a collar and a proboscis. Example, 

 balanoglossus. 



Subphylum CRANIATA or VERTEBRATA ( ). 



Chordates in which the notochord either persists or becomes invested 

 with cartilage. Vertebrates have a segmented spinal column. 



Class CYCLOSTOMATA ( ). Eel-like 



vertebrates without functional jaws or lateral appendages. Examples, 

 hagnshes and lampreys. 



Class PISCES or GNATHOSTOMATA ( ). 



Fishes with a lower jaw and paired pectoral and pelvic fins, scales and 

 paired nostrils. The heart has an auricle, a ventricle, a conus arteriosus, 

 and a sinus venosus. 



Class AMPHIBIA ( ). Cold-blood vertebrates 



breathing by means of gills at some stage of their life-cycle. Skin not 

 usually covered with scales. Three chambers in heart beside the conus 

 arteriosus and sinus venosus. Frogs, toads, newts, and salamanders. 



Class REPTILIA ( ). Cold-blooded 



vertebrates breathing by means of lungs throughout their life-cycle. 

 Usually covered with scales. Lizards, snakes, crocodilians, and turtles. 



Class AVES ( ). Warm-blooded vertebrates, 



whose body is usually covered with feathers and the fore-limbs modified 

 for wings. Heart of four chambers. Birds. 



Class MAMMALIA ( ). Warm-blooded 



animals with hair covering at some stage in their life-cycle. They suckle 

 their young and have a diaphragm between thorax and abdomen. 



Subclass PROTOTHERIA ( ). Egg-laying 



mammals. Example, monotremes, such as the Australian duck-bill. 



Subclass EUTHERIA ( ). Mammals which 



give birth to living young. These are the true mammals. 



Division DIDELPHIA or METATHERIA ( ). 



These are the marsupials, such as the opossum and kangaroo. 



Division MONODELPHIA ( ). These are the 



placental animals which are nourished in the body of the mother through 

 a true placenta. 



