Dr, H. Burraeister on Saurocetes arsrentinns. 53 



&'^ 



it is figured in my ' Annals of the Public Museum of Buenos 

 Ayres,' torn. i. pi, 26. fig. 2. 



The superior part of the anchylosed portion of the jaw con- 

 tains the alveoles for the teeth, whereof there are on the left 

 side twelve, and seven on the right, wanting the hinder por- 

 tion of this side of the jaw before the separated articular 

 branch. Each alveole reproduces completely the figure of the 

 roots of the teeth ; it is, like them, divided at the lower end 

 into two branches, and united by a very small short passage 

 with the alveolar channel in the interior of the jaw (fig. 2). 

 As some of the alveoles are open in the broad portion of the 

 right side of the jaw, I could see the whole figure of them very 

 clearly, and distinguish well the small and very short passage 

 leading into the open channel of the interior of the jaw. In 

 this hinder region of the anchylosed portion of the jaw, where 

 the alveolar channel is much larger, even the tips of the roots 

 of each tooth pass into the channel, so that they are seen like 

 protuberances on the superior, larger side of the channel. 



The upper surface of the anchylosed portion of the jaw be- 

 tween the teeth is moderately convex, with a median im- 

 pressed line as the remains of an anterior suture which has 

 united the two half-jaws to each other. On the opposite or 

 lower sm-face no trace of suture is visible in the anterior por- 

 tion of the jaw; but it is sufficiently conspicuous at the hinder 

 end, before the separation of the two articular branches. The 

 outside of the jaw is peculiarly wrinkled, and furnished with 

 a very well-marked furrow on each side along the lower region 

 (see tig. 1), which is narrower and deeper at the anterior end. 

 From this furrow the wrinkles begin in an oblique direction, 

 ascending from behind forwards, and growing somewhat smaller 

 and less strongly marked. The furrow does not continue fur- 

 ther back than to the end of the anchylosed portion, vanishing 

 here completely. But the two articidar branches have also 

 similar but more horizontal wrinkles on the outside, as shown 

 in figs. 1 & 4. It is worth notice that some of the Delphinidje, 

 like Pontoporia (see my figure, I. c), have the same furrow on 

 the anchylosed portion of the under jaw. 



With respect to the teeth, the generic character of the ani- 

 mal is founded on the circumstance that all the teeth are of 

 the same form, and not different, like those of Zeuglodon or 

 Basilosaurus. In a paper published at Halle in 1847*, I 

 have shown by figures that Zeuglodon has at least three dif- 

 ferent forms of teeth : — one with single crown and root ; a 

 second with a great conoidal crown to which are attached one 



* Bemerkimgen iiber Zewjlodon cetoides, Owen, Basilosaurus, Harlan, 

 Hydrarchus, Koch, cftc. 4to, with figure. Halle : Sch'vetzke & Sohn, 



