Tertiary. | PALAONTOLOGY OF VICTORIA. (Mammalia, 
Prates XLI. anp XLII. 
ARCTOCEPHALUS WILLIAMSI (McCoy). 
[Genus ARCTOCEPHALUS (F. Cuy.). (Sub-kingd. Vertebrata. Class Mammalia, Order 
Fere. Fam. Phocide.) 
3—3 1-1 6 — 
6 
Gen. Char,—Dental formula :—i., 9; ¢-, To1i™ = 36.— Upper jaw: Inci- 
5—5 
sors, 2 inner, on each side, small, crowns bifid by a transverse notch ; outer one like a canine, two 
or three times larger than middle ones. Canines large; molars six, when young, cingulum on 
inner side of base ; roots large, fangs connate. Lower jaw: 4 incisors, small, not notched ; canines 
large, compressed ; molars 5, shaped as in upper jaw, roots of fifth slightly divaricated. 
Muzzle tapering to front. Palate bones rather short, reaching only to middle of zygomatic arch. 
Ramus of lower jaw narrow, with a crest-like process on hinder part of lower edge in front of 
condyle. ] 
Description.—The old male skull, on which the A. Williamsi is founded, has 
the occipital crest well developed. It most nearly approaches the living Australian 
Hared Seal, the Arctocephalus lobatus, in the semi-elliptical posterior edge of the 
palate, and its backward extent; but differs in the larger roots, and very much smaller 
crowns of the molars, and in the much smaller relative size of the anterior and pos- 
terior lobes or cusps, as well as in the lower and less acute middle lobe. The canines 
are also larger and usually greatly worn by lateral oblique abrasion ; the outer canine- 
like large upper incisors (7. 8) appearing relatively smaller. The forehead is much 
wider across the postorbital processes ; the pre-maxillaries extend relatively farther 
back, and the zygomatic process is broader, the arch rather flatter, and especially the 
suture between the zygomatic portion of the squamosal is much less oblique, the 
consequent more forward extension of this bone in the A. Jobatus and the general 
slenderness of the arch being conspicuously different from the fossil one. Leneth of 
skull from anterior edge of incisor alveolus to posterior edge of occipital condyles, 
1 foot. Taking this leneth as 100, the following proportions are found:—Length to 
middle of posterior notched edge of palate, 475 (A. lobatus, ''5) ; from anterior edge 
of incisor alveolus to hind edge of glenoid cavity, 68, (A. lobatus, 735); greatest 
width of skull opposite middle of glenoid fossa, 34°; (A. lobatus, -%%); length of 
lower jaw, 56°, (A. lobatus, =%},) ; depth of lower jaw vertical at front edge of m.°, 
a8, (A. lobatus, 345); from lower edge of basioccipital to top of supraoccipital 
crest, 4, (A. lobatus, 45); width across from tip of one postorbital process to 
the other, 336, (A. lobatus, -%3,); from front edge of incisor alveolus to posterior 
superior end of pre-maxillary bones, 33,4; (A. lobatus, 3265). 
In Dr. Gray and Mr. Gerrard’s catalogue of bones of the Mam- 
malia in the British Museum, the genera Arctocephalus and Otaria 
6—6 é : 
* Dr. Gray gives 6—6 38 the molar formula for Arctocephalus in all his treatises on 
Seals, but it is obviously by error that more than five should be indicated on each side in the 
lower jaw. The hindmost upper molar often disappears with age, as in our fossil. 
aia 
