File:History of North American pinnipeds - a monograph of the walruses, sea-lions, sea-bears and seals of North America (1880) (14764179772).jpg

Identifier: historyofnortham00alleuoft (find matches)
Title: History of North American pinnipeds : a monograph of the walruses, sea-lions, sea-bears and seals of North America
Year: 1880 (1880s)
Authors: Allen, J. A. (Joel Asaph), 1838-1921
Subjects: Pinnipedia -- North America Mammals -- North America
Publisher: Washington : G.P.O.
Contributing Library: Earth Sciences - University of Toronto
Digitizing Sponsor: MSN

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
. narrowed just behind the orbital fossse to less than half thebreadth they present in the Atlantic Walrus, and extend furtherposteriorly in a narrow point instead of being rather abruptlytruncated. In the Atlantic species, the lateral anterior angleof the frontals is in a line with the most laterally projectingportion of the maxiUaries, Av^hile in the Pacific species thebreadth at this point is considerably greater than at the ante-rior border of the frontals. While the frontals present in eachspecies a considerable range of variation in resi^ect to their pos-terior outlines, the average difference is very nearly as here rep-Misc. Pub. No. 12 11 162 ODOB^NUS OBESUS PACIFIC WALRUS. resented. The young skulls here compared are of nearly thesame age; but unfortunately the absence of the occipital por-tion of the skull in the only Pacific specimen of this age (Fig.22) I am able to figure renders it impossible to compare by fig-ures the occipital region in young specimens. Other specimens
Text Appearing After Image:
Fig. 22.—Odobienus oiesus. Fig. 2^.^OdoI>a;nns rosmarus. young enough to have the sutures still open show the differ-ences seen in the occipital region of older skulls. Another difference, but one apparently less constant than theothers, is the presence in the young skull of the Pacific Walrus(Pigs. 22 and 24) of an extension posteriorly of the intermaxilla-ries for two-thirds of the length of the nasals. In the Atlanticskull (Pigs. 23 and 25), the intermaxillaries do not enter into thedorsal outline of the skull, but terminate at the anterior bor-der of the nasals. This difference is open to exceptions, and isnot offered as a character of importance, since the same modifi-cation or backward prolongation of the intermaxillaries occursoccasionally in the Atlantic species, and is sometimes absent inthe Pacific S)3ecies, while in some examples the intermaxillariesreach the dorsal surface only as isolated ossicles between thenasals and maxillaries. As a rule, however, the conditions

Note About Images