250 TEETIAET YEETEBEATA OF THE EATtM. 



that Fraas's restoration of the snout is correct) the distance of the posterior border of 

 the nares from the occipital crest would be represented by 70, in Prozeuglodon- by 

 63, and in Zeuglodon osiris by 51. Other points in which this skull differs from that 

 o£ Protocetus are: (1) the rostrum is much broader and more massive, and does not 

 narrow suddenly in front oijom. 3 ; (2) the nasals are rather shorter and are separated 

 posteriorly by a process of the frontals; (3) the supraoccipital surface is perhaps a 

 little less concave from side to side. From the skull of Zeuglodon osiris this form is 

 also distinguished by: (1) a relatively rather stouter rostrum and generally more 

 heavily built skull ; (2) the possession of much longer nasals, separated posteriorly 

 by a process of the frontals — this nasal process of the frontals does, however, exist in 

 some species of the genus (see J. Miiller, pi, vii. fig. 2) ; (3) having a very much 

 less concave supraoccipital surface ; (4) the greater inflation of the cranial region 

 of the skull. 



A plaster cast of the brain-case, taken from an imperfect skull, agrees fairly well, 



Text-fig. 82. 



Palatal view of left premaxilla and maxilla, with pm. 3 and pm. 4, of Prozeuglodon atrox. 



c, alveolus of canine ; /., fossae for the reception of the points of the lower teeth ; i. 1-3, alveoli of the 

 incisors ; i.r., inner roots oipm. 3 and 4 ; m. 1, first molar ; ma;., maxilla ; pm. 1-4, premolars or their 

 alveoli ; pmx., premaxilla ; s., suture for union with palatine, g nat. size. 



SO far as it goes, with a natural brain-cast described by Dr. Elliot Smith in his paper 

 on the " Brain of the Archseoceti " *. In this he states that the natural cast differs so 

 far from the artificial cast taken from a skull of Zeuglodon osiris that it must have 

 belonged to an animal differing generically from that form. 



Upper Dentition (PL XXI. figs. 1a, 1b ; text-fig. 82). — There are three incisors, 

 which, judging from one of which the crown is well preserved, were conical sharp- 

 pointed teeth directed somewhat forwards. The crown is somewhat compressed 

 laterally, and there is a slight keel on the anterior and posterior borders ; the enameL 

 at the base of the crown is raised into fine ridges. The first incisor is situated at the 

 extreme anterior end of the premaxilla, the others follow at intervals of about 1'5 cm. ; 



* Proc. Eoy. Soc. vol. 71 (1903) p. 322. 



