256 TEETIAET TBETEBEATA OP THE EAYtTM. 



uncertain whether this had two or three roots. In the mandible the only teeth preserved 

 are the three posterior premolars. Figured PI. XXI. In the following table the 

 dimensions (in centimetres) o£ this skull are placed in the first column, the corresponding 

 measurements in Protocetus atavus according to B. Fraas, and in Zeuglodon osiris 

 according to Stromer, being given in the second and third columns respectively : — 



Prozeufflodon Protocetus Zeuglodon 



airox. atavus. osiris. 



Length from the end of the snout to the occipital crest 60 60 70 app. 



J, „ „ ,, foramen magnum 61 app. 58 68 



„ from hinder border of the narial opening to the occipital crest . 36 42 36 



„ of the narial opening 7 app. 7 



Breadth of the narial opening 3'8 2-5 



Length from the posterior border of the frontals to the occipital crest . 16-5 app. 20-5 



Width of the skull at the narial opening 9-4 4-3 



„ V at the supraorbital expansion 24-5 16-7 24 (?) 



,, ,, between the temporal fossae 4-5 3-3 



„ „ at the zygomatic process 34 app. 24 28 (?) 



Height of occipital surface above the upper edge of the foramen magnum. 11-8 8 13 (?) 



Width between outer ends of condyles 11 app. 



„ of foramen magnum 5 app. 2'6 



Length of premaxilla 29 30 34-5 



nasals 16-2 18-5 16 



Greatest breadth of nasals taken together 4'5 2'5 4-4 



Distance between jugal and posterbital process of frontal 2-5 



The dimensions (in centimetres) of the upper teeth (or, where absent, of their 



alveoli) : — 



Length. Width. 



i. 1 (at alveolus) 1-8 1-2 



i.2 „ 2-3 1-4 



i.3 „ 1-9 1-3 



c. „ 2-7 1'8 app. 



pm.l ? ? 



i>m.2 4-7 1-3 



jpm.S 4-5 1-8 



j>m.4 3-7 1-7 



TO. 1 3-1 1-8 



Length of incisor series 9 cm. Length of premolar series 18'2 cm. 



M. 9266. Portions of a much broken skull, including the posterior (cranial) region, the frontal 

 expansion, the maxilla^ and the premaxilla ; the last contains no teeth, but in the 

 maxilla pm. 3, pm. 4, and part of m. 1 are still in situ, and show the three roots of 

 the premolars (text-fig. 82). The cranial region is interesting, because nearly all the 

 sutures remain open, and the structure of the occipital region is well shown (text-fig. 81). 

 From this specimen a brain-cast similar to the natural brain-cast described by 

 Dr. Elliot Smith* has been made (M. 9265). The dimensions (in centimetres) of 

 this specimen are : — 



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



