126 DE. C. W. ANDEEWS OX THE [May I 907, 



bone, which is inclined somewhat forwards ; above, its border is 

 continuous with the outer edge of the pedicle of the neural arch, 

 below which it bears a blunt diapophysial projection (d.) ; ventrally 

 it is produced downwards into a stout parapophysial process (p.), 

 oval in section and projecting considerably below the ventral border 

 of the centrum. The middle of this plate of bone is perforated by 

 the, relatively small and nearly circular, vertebrarterial canal (v.c), 

 which measures about 8 or 9 millimetres in diameter. Judging 

 from the figures of the vertebrae of Protocetv.s given by Prof. E. 

 Eraas, 1 the vertebra here described must be either the fifth or the 

 sixth, most probably the latter. 



The dimensions of the specimen are : — 



Centimetres. 



Width of the centrum 55 



Height of the centrum 4*5 



Length of the centrum 2*05 



Greatest width between the ends of the diapophyses ,. 10'5 



Greatest width between the ends of the parapophyses 10*4 



Extreme height from the bottom of the parapophyses to the top 



of the neural spine ... 11*8 



Width between the anterior ends of the prezygapophyses 8*5 



Width of the neural canal 3*3 



Height of the neural canal 2*8 



Vertical diameter of the vertebrarterial canal 0*8 



This specimen, having been found in the same locality and horizon 

 as the type-specimen of Zeuglodon WanJclyni, maybe referred with- 

 out much doubt to that species, the skull of which is distinguished 

 from that of other species by the shortness of the maxilla, the 

 shorter distances between the teeth, and the posterior flattening of 

 the sagittal crest. Dr. Stromer has compared it with Z. Osiris from 

 the upper beds of the Middle Eocene of the Fayum, and shows that, 

 although the two differ in the above-mentioned points, they resemble 

 one another in many others, as, for example, in the presence of two 

 single-rooted teeth, c. an&pm. 1, in the maxilla, and in the dimensions 

 of the premolars. 



It is now almost certain that the Zeuglodon ts arose from a 

 Creodont ancestor on the northern shores of the Ethiopian land in 

 the early part of the Eocene Period, the ancestral forms at present 

 known being Protocetus from the Mokattam Hills and Prozeuglodon 

 from the Fayivm. By the end of the Middle Eocene the true 

 Zeuglodonts had come into existence, and had spread rapidly over the 

 earth, their remains being found in the upper part of the Eocene 

 of America, England, and Xew Zealand. The presence of members 

 of the group in the two first-mentioned regions seems to show that 

 the ocean extended, as now, from the Mediterranean to the American 

 continent, while the presence of Zeuglodon-bones associated with a 



1 ' Keue Zeuglodonten aus dem unteren Mitteleocan von Mokattam bei 

 Cairo ' Geol. & Palaont. Abhandl. n. s. vol. vi (1904) pi. xi, figs. 1-9 & pi. xii r 

 figs. 1-9. 



