58 THE VOYAGE OF H.M.S. CHALLENGER. 



Phoca. 



Callocephale, F. Cuvier, Mem. du Museum, t. xi. p. 182, 1821 



Infraorbital foramen opens into anterior part of floor of orbit, which slopes backwards 

 to become continuous with the thin posterior border of zygomatic root of maxilla. 

 Anterior nares not high, post-canines with more than a single cusp on the crown, mostly 

 three-cuspidate ; fangs two-rooted except in the first post-canine. 



Phoca vitulina, Linnseus. Common Harbour Seal. 1 North Atlantic Ocean. 



Phoca vitulina, Linn., Syst. Nat., ed. x. p. 38. 

 Callocephalus vitulinus, Gray, Brit. Mus. Catal., p. 20, 1866. 



Nasal bones elongated and attenuated between frontals, not ankylosed together ; 

 premaxilla forming side of anterior nares but usually not quite reaching the nasal ; 

 neither antorbital nor postorbital processes ; occipital ridge fairly marked ; sagittal 

 ridge indicated ; no ridge along line of sagittal suture. Hard palate with posterior 

 border acutely cleft, the sides of cleft forming with line drawn between hamular- 

 pterygoids almost an equilateral triangle; the apex of the cleft a little behind the 

 posterior edge of the maxillary root of the zygomatic arch and considerably in front of 

 the hamular-pterygoids ; posterior border of vomer visible _ in cleft and articulating with 

 vomerine crest ascending from the upper surface of the anterior part of the horizontal 

 plate of the palate bone. Zygomatic arches bulging, and their greatest width, which is 

 about the middle, considerably exceeding the greatest cranial width. Post-canines set 

 closely together and obliquely, so that the posterior part of the tooth in front is external 

 to the anterior part of the tooth immediately succeeding. Subcondyloid process of 

 posterior border of ramus of mandible short, inverted, distinct from the tubercle at the 

 angle of the bone ; lower border of horizontal ramus scarcely inverted ; coronoid 

 moderate. 



Phoca grcenlandica, Fabricius. Harp Seal. North Atlantic 2 and Arctic Oceans. 



Phoca grcenlandica, Fabricius in Muller, Zocl Dan. Prodr., p. viii., 1776, and Fauna groen- 

 landica, p. 11, 1780. 



Nasal bones elongated and attenuated between frontals, not ankylosed together. 

 Premaxilla forming side of anterior nares and articulating with about one-third of outer 

 border of nasal but not reaching its tip. Anterior nares oblique, but the lateral borders 

 more concave near the nasal bones than in Phoca vitulina, Phoca hispida, and Phoca 



1 In writing the descriptions of the characters of the skulls of the several species of Seals I have as far as possible 

 selected those of adult males. 



2 In November 1874 I recorded (Journ. Anat. and Phys., vol. ix. p. 163) the capture of a Seal on the coast of 

 Lancashire, which was identified by Mr. T. Gough and myself as Plwca grcenlandica. 



