EXTERNAL CHARACTERS. 693 



four and a half feet long, killed July 20, was dark-gray above, 

 along the back still darker or blackish-gray, and paler on the 

 sides; back and sides with irregular spots of black of various 

 sizes ; nose and limbs brownish-gray, unspotted.* 



Edmonstonet gives the weight of this seal as "45 stone of 

 14 pounds each" (= 630 pounds), and its length as "10 to 12 

 feet." 



SKULL. The two skulls before me indicate great variations 

 resulting from, age, especially in the thickening of the bones 

 and the development of heavy sagittal and occipital crests. 

 The old skull (No. 4717, Nat. Mus., Sable Is!., N. S.), is pre- 

 sumably that of a very old male, and differs from any which I 

 have seen figured in its large size and greatly produced crests. 

 The teeth in the young, especially in the lower jaw,f have 

 slight but distinct accessory cusps, which become wholly ob- 

 literated later in life. In the old skull already mentioned the 

 crowns are much worn, and the roots are very thick and strong. 

 The strongly marked distinctive features of the skull have 

 already been noticed (antea, p. 683). In all probability the sex- 

 ual differences are strongly marked, especially in weaker struc- 

 ture and slighter crests in the female. To judge by BalPs fig- 

 ure (1. c., pi. ii) of the skull said to be that of a very aged female, 

 they may be wholly lacking. I subjoin the following measure- 

 ments of the two above-mentioned skulls : 



*Apud Wagner, Schreber's Saugthiere, Band vii, 1846, pp. 15, 16. 



tA view of the ancient and present state of the Zetland Islands, etc., vol. 

 ii, 1809, p. 294. 



t See Ball, Trans. Roy. Irish Acad., xviii, pi. iii. 



$ I regret especially in this connection my inability to consult Hornschuch. 

 and Schilling's " Kurze Notizen tiber die in der Ostsee Vorkommenden Arten 

 der Gattung Halichoerus, Nilsson." Greifswald, 1850. 



