8. Soft-bodied animals enclosed or partially enclosed in a shell 

 MoUns\s (Chapter 6) 

 Not so 9. 



9. Colonial animals, usually appearing moss-like or jelly-like 

 MosS'li\e and JeUy'li\e Animals (Chapter 3) 

 Single individuals 10. 



10. With fins or with a wide fold of skin forming a fin-like tail 11, 

 Without fins or a fin-like tail 12. 



11. No gill openings on sides of head; head and body so closely joined as to 



be oval; no side fins 



Frog and Toad Larvae, Tadpoles (Chapter 10) 

 With one or more gill openings present on each side of the head; body 

 lengthened; side fins present in most cases 



Fishes and Lampreys (Chapter 8) 



12. With definite scales or plates on top of the head and usually on the body 



Sna\es and Legless Lizards (Chapter 12) 

 No scales 13. 



13. Body segmented (segments sometimes evident only on the under side) 14. 

 Body unsegmented 15. 



14. With a definite head, often darker than the body; usually with external 



biting or sucking mouth appendages 



Arthropods, Insect Larvae (Chapter 7) 

 Head not readily distinguishable; no such mouth appendages (except in 

 one large semi-marine worm) 



Worm'li\e and Leech'li\e Animals, Annelids (Chapter 5) 



15. Without tentacles; no breathing pore on the side 



Worm-hl^e and Leech'li\e Animals {other than Annelids) 

 (Chapter 5) 

 With tentacles; with or without a breathing pore on the side 16. 



16. With a ring of tentacles around the body; no breathing pore; found in 



water 



Moss4i\e and Jelly 4i\e Animals, Coelenterates (Chapter 3) 

 With two pairs of tentacles on the head and a breathing pore on one 

 side; found in moist places on land, not in water 



Molluscs, Slugs (Chapter 6) 



KEY TO THE PRINCIPAL LARGE GROUPS OF VERTEBRATES, 

 BASED ON SKULL CHARACTERS 



1. Bones overlapping and covered with striations radiating from the center 



of each bone 

 fish 

 Bones more or less dovetailed or with sutures (junctions) not evident 2. 



2. Two occipital condyles (knobs on either side of the large opening on 



back of skull, for attachment of the first segment of the backbone) 3. 

 One occipital condyle, usually below the large rear opening 6. 



25 



