54 Dr. H. Burmeister ow Saurocetes argentinus. 



or two smaller cones, and a subdivided root on the end ; and a 

 third class of large molars, with two great equal roots and a 

 higher compressed crown of from six to nine conoidal knobs, 

 of which the central one is the most prominent and highest. 

 It seems probable that the first class of teeth with the single 

 crown were the foremost, the second the following on each 

 side (corresponding to the false molars), and the third class 

 the true molars of the hinder end of the series. In our Sauro- 

 cetes no such diflerence occurs ; all the teeth are of the same 

 form, corresponding in structure rather to the second class of 

 the teeth of Zeuglodon than to the first and third. Every 

 tooth has a single conoidal crown, somewhat curved backward 

 and compressed on both sides, covered, like the teeth of Zeu- 

 glodoHj with a distinct layer of enamel, irregularly wrinkled 

 on the external surface, as may be seen in fig. 3, which shows 

 one tooth of the natural size*. Below the crown is a small 

 and narrow cingulum, corresponding to the part of the tooth 

 enclosed in the gum and outside of the jaw ; a similar cingu- 

 lum is also seen in the second class of teeth of Zeuglodon (see 

 my cited account, fig. 7). Below this cingulum begins the 

 root, enclosed in the alveole of the jaw, like a turnip, at first 

 somewhat thickened and soon after more compressed from the 

 sides, descending in the interior of the jaw, with two branches 

 separated only at the end, which diverge somewhat from each 

 other. The first or anterior is always somewhat thicker, but 

 shorter ; the second longer, thinner, and more prominent, is ge- 

 nerally accompanied by another small knob at the beginning. 

 Tlie whole tooth is 2 inches high, of which the crown measures 

 8 lines, the cingulum 1^ line, and the root 15 lines. All the 

 nine teeth present in the jaw (namely, six on the left side and 

 three on the right side) are of the same figure, without any 

 difference except in size, the posterior teeth being somewhat 

 smaller, as is also the case in the teeth-series of the living 

 DelphinidEe. 



The portion of the articular branch of the right side figured 

 in PI. I. fig. 4 begins with the alveole of the last tooth, and is 

 from that point 5 inches long. Under the alveolar groove the 

 piece is 2g inches high, and 1^ inch broad, enclosing an open 

 channel \\ inch high and | inch broad. From this point the 

 jaw enlarges more and more behind, so that the fragment ter- 

 minates with a height of Sj inches and a width of 1| inch, 

 with an open cavity in the interior 2f inches high and 1^ inch 

 broad. The osseous substance forming the branch is much 

 thicker at the anterior than at the hinder end, measuring there 



* In the plate the figure of the tooth is eiToneously stated to be half 

 the natural size. 



