Tertiary.^ PALAEONTOLOGY OF VICTORIA. ^Mammalia. 



Plates XXXI., XXXII., and XXXIII. 

 DIPROTODON LONGICEPS (McCoy). 



[Genus DIPROTODON (Ow.). (Sub-kingd. Vertebrata. Class Mammalia. Order Mar- 

 supiata). 



3—3 0—0 2—2 3—3 



Gen. Char. — Dental formula : — i., ^ _ ^ ; c, ^ _ ^ ; d.m., ^^^ ; m., g _ ^ . Incisors, 6 



(3 on each side) in upper jaw ; anterior pair broad, arched, scalpriform, and longitudinally 

 sulcated ; lateral pairs much smaller ; 2 in lower jaw nearly straight, sub-cylindrical, obliquely 

 worn at tip. Molars, each with two transverse prominent ridges, and usually a small basal ridge 

 in front, and one behind ; fangs large, branched. Anterior grinder (rf. 3) shed at an early age. 

 Surface enamel of all the teeth minutely rugose, with flexuous vermicular ridges, and inter- 

 vening irregular pores.] 



Description. — Lower incisors: Perfectly straight, with no trace of the upward 

 curvature of D. Australis (Ow.*) ; length, 13| inches (D. Anstralis only 10 inches) ; 

 circumference at emergence from socket (5 inches from tip), 5 inches 3 lines : 

 longitudinal extent of worn surface, 3 inches; greatest width, 1 inch 1 line, heing 

 as long as, hut narrower and more ohiique than, the same part of D. Australis ; 

 the wearing is in three planes corresponding to the three upper incisors opposed to 

 it on each side : transverse section at point of emergence from socket oblong, with 

 obtusely rounded angles; vertical diameter, 1 inch 11 lines; transverse diameter, 

 1 inch 5 lines; outer side slightly concave longitudinally above the middle, other 

 sides slightly convex ; less than two-thirds of the incisor is in socket, which extends 

 backwards to vertical with line separating first molar from last premolar ; surface of 

 enamel with minute irregularly contorted vermicular longitudinal vs^rinkles and inter- 

 vening irregular small pits and pores. — Diastema : From anterior upper edge of 

 incisor socket to second molar {d. 4), 6 inches, and is consequently much longer 

 than the corresponding part in D. AustraUs, which is only about 4^ inches, and 

 it rises at a much smaller angle as it recedes from the incisor. First molar (d. 3) 

 has been shed from age in our specimen, its place being indicated by a small pro- 

 tuberance in front of the next tooth seen in our plates XXXI. and XXXII., figs. 1 

 and la. — Second molar {d. 4) : Antero-posterior diameter of base, 1 inch 2 lines, 

 thus much smaller than similar old worn examples of D. Australis, which are 



1 inch 8 lines (Ow. Op. Cit., t. 40, fig. 4), and in our species the great anterior 

 and hind basal ridges, if they ever existed, are worn quite down ; greatest transverse 

 diameter (near hinder edge), 11 lines, while the corresponding part in a similarly 

 aged tooth of D. Australis is 1 inch 2 lines. The smallest unworn corresponding 

 tooth (said to be a young female from Victoria, Ow. Op. Cit., t. 40, fig. 2) is 1 inch 

 5 lines in fore-and-aft extent. — Third molar {m. 1) : 1 inch 9 lines in fore-and-aft 

 extent, and 1 inch 1|^ lines in greatest transverse diameter; both the anterior and 

 posterior basal ridges are smaller than in D. Australis, the anterior one being 

 scarcely perceptible, and the posterior one forming a short prominent high part in 

 the middle, deeply indenting the middle of the anterior margin of the next tooth 

 behind, and then sinking rapidly to a lower level on the outer and inner sides. — 

 Foicrth molar {m, 2) : Fore-and-aft length at base of crown, including the ridges, 



2 inches 2 lines ; greatest width, 1 inch 6 lines (corresponding measurements of 

 homologous tooth in D. Australis, Ow. Op. Cit., t. 40, fig. 11, 2 inches 6 lines, and 

 1 inch 9 lines). Besides its smaller size and narrower proportion indicated by the 



* Phil. Trans. 1870, t. 37, f. 4. 

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