16. Incisors 10/8; two large oval openings in palate between cheek teeth; 



very small brain case with large occipital crest 

 Didelphis Opossum 

 With less incisors; palatal openings, if any, small 17. 



17. Canine teeth about twice as long as others; incisors small (Carnivores) 



18. 



Canines little, if any, larger than other teeth, or very small skulls with 



a gap in front part of upper jaw 42. 



18. Skull almost as wide (from one zygomatic arch to the other) as long; 



post-orbital bar almost complete; cheek teeth 4/3 or 3/3 (Cat Family) 



19. 



Skull length one and one-half times, or more, the zygomatic width; post' 



orbital bar quite incomplete; more cheek teeth usually present 20. 



19. Maxilla making contact with one-half the length of nasal; four upper 



cheek teeth (first and fourth very small) on each side 

 FeJis Cat, Panther 

 Maxilla making only slight contact with nasal; three upper cheek teeth 

 on each side 



Lynx Lynx and Bobcat 



20. Ear canal opening directly to side of skull; inner part of last cheek tooth 



not markedly wider than outer part; most animals in this group with 

 a skull four inches or more in length 21. 



Ear canal slanting forward; inner part of last cheek tooth definitely 

 wider than its outer part; usually small skulls, rarely over four inches 

 long Weasel Family 33. 



21. Teeth all relatively small, cheek teeth peg-like or with three points, and 



of less diameter than the canine tooth; outer incisors definitely larger 

 than the inner Seals and Sea-lions 22. 



Teeth of good size, at least three of the back cheek teeth touching their 

 neighbors and with well developed cutting or grinding surfaces; in' 

 cisors not differing greatly in size 25. 



22. Cheek teeth set diagonally in jaw, small and with three points; upper 



incisors pointed; cranium very wide and flat 

 Phoca Harbor or Hair Seal 

 Cheek teeth not definitely three pointed; upper incisors notched; cranium 

 sometimes with a ridge on top 23. 



23. Nose pointed; cheek teeth almost or quite touching; males with a very 



high crest on cranium 



Zalophus Sea Lion 

 Nasal region high, giving the skull a rectangular appearance when 

 viewed from the side; cheek teeth not touching 24. 



24. Fifth upper cheek tooth separated by about three-quarters of an inch 



from the fourth 



Eumetopias Northern Sea Lion 

 Upper cheek teeth evenly spaced 

 Callorhinus Fur Seal 



25. Skull usually ten inches or more in length; nasal bones not touching the 



maxillary bones Bear Family 26. 



526 



