264 THE AMERICAN NATURALIST. . [Vor. XXXV. 
EXPLANATION OF PLATE I. 
Illustrating the patterns of the upper molar teeth in marsupials and their 
probable sc d relations. 
Notre. — The prototypal form is atas: represented by Peratherium. 
Figs. b and c are inserted for comparison 
a.— Peratherium fugax Cope. f. — Petauroides volans 'Thos. 
b. — Didelphys azare Temm. g.— Thylacinus cynocephalus Fisch. 
— Didelphys virginiana Kerr. h. — Trichosurus vulpecula Jent. 
d. — Dasyurus viverrinus Shaw. i. — Macropus sp. 
e. — Perameles nasuta Geoff. j-— Phascolarctos cinereus Fisch. 
Abbreviations. 
Pr. — protocone. Me. — metacone. 
a. — paracone. Hy. — bypocone. 
J 
St. — external styles. 
Fic. b, after Giebel (Odontographie, Taf. XVII, Fig. 10, a). 
