DR. J. MURIE ON THE ANATOMY OF THE SEA-LION. 507 
They apply to the skull figured by me in Pl. LXXVII. figs. 16, 17, which is that 
numbered 5968, Cat. Coll. Surg. Besides the points here displayed in palatal views, a 
comparison of the crania in the accompanying Pl. LX XVII. further bears out state- 
ments concerning said differentiations’. 
g. Progressive Cranial changes—Although writers previously had incidentally ad- 
verted to an alteration in the form of the skull with age in some of the Eared Seals, yet 
no one has so forcibly pointed this out as Dr. Gray*. In one of his papers on the 
Otariade he justly remarks*:—* The skull of these animals changes so much in form 
as the animal arrives at adult and old age, that it is not always easy to determine the 
species by it, unless you have a series of them of different ages and states to compare.” 
So much do the parietal crest and other osseous prominences shoot forth in the 
Sea-bear or Great Sea-lion of some travellers (Otaria jubata), that between young and 
old specimens changes as great and characteristic as obtain in the cranium of the 
Gorilla occur in them. 
In tracing the development of the skull of this species of Otaria, 1 have had the 
advantage of comparing side by side a large number of both sexes and various ages. I 
tabulated a series of proportional measurements of the relative growth of different 
regions, but refrain from introducing the table in this place. Instead I have illustrated, 
in Series Pl. LXXVII., examples of five different stages of the development, to each of 
which I append remarks. My figures have been drawn to a uniform scale, quarter 
natural size; I nevertheless subjoin, in inches and tenths, the absolute length, breadth, 
and height of each, for greater precision. 
| 7 | 
Ist stage. |, drd stage. Sth stage. 
=, >, \2nd stage. 2 4th stage.” 
Crania of Otaria jubata. ee | Yearling. 3 ag Gee ), 3 old. | on iL ry 
ee ees aes | = a 
Nos. in Cat. Coll. Surg., except sp. 3rd column | 3971c. | 39718. Z.S.sp.| 3968.) 39714. | 3971. 
Greatest length, premaxilla to condyle ...... 6:5 85 10-6 | 11:0 128 | 1438 
Greatest Preadthir an .w a. arejete vit ole dies vre'ele > 39 46 65 | 58 Toga Of 
Greatest, height, without mandible line cutting 3-6 4-0 46 AT 6:0 | 8-2 
SH ALOU Wonca shes terateione sista icia1e.cseieus'e: v= 20 
| 
First stage. In the young skull of a few weeks old the brain-region is in prepon- 
ridges into a parietal crest, nor any considerable development of the occipital ridge. The boundary of the 
large mastoid is well shown in this skull, together with the share which the paroccipital takes in this rough 
muscular ridge external to the petrosal. The middle surface of the basioccipital is less carinate than in the 
male. The entry of the carotid canal in the petrosal is more distinct from the jugular vacuity. The broad 
superorbital processes of the frontal are less angular. The canines and external incisors of the upper jaw are 
smaller in comparison with the molars. The first and second incisors have bifid crowns. The angle of the 
lower jaw is produced and bent inwards more than in the male.” 
1 T may also refer to a most valuable communication “On the Eared Seals,” by Mr. J. A. Allen, Bull. Mus. 
Comp. Zool. Camb. U.S. vol. ii. no. 1 (1870-71), wherein the author, with occasionally sweeping criticism, has 
most adroitly woven together many facts concerning sexual variation and changes of the skull in the North- 
Pacific species. 
2 Pp. Z. S. 1859, p. 360, and Cat. of Seals and Whales in B. M. ‘ Ann. & Mag. Nat. Hist. 1868, i. 100. 
