52 Dr. H. Burmeister on Saurocetes argentinus. 



aud also the occipital part of a skull, which has so much 

 resemblance to that of Anoj)lothermm grande (Blaiuville, 

 Osteogr. pi. 8) that we may infer the existence of this Tertiary- 

 form in South xlmerica during the Later Tertiary epoch. 

 Bravard, in his 'Mouografia' of the formation (Parana, 

 1858, p. 45), mentions the same genus, represented by a first 

 molar tooth of the animal ; and I must confirm his discovery 

 as veiy probable by the part of the skull in my hands, which, 

 unfortunately, has no teeth, but only the occipital, parietal, 

 and the mastoid portion of the temporal bone complete. 



Marine Mammalia are rare. Bravard describes some por- 

 tions of a whale {Balfsna duhia, p. 34) as the only marine 

 mammiferous animal known to him. I had the good fortune 

 to find, dm-ing my residence in Parana, the tooth of an Otaria 

 (Reise, i. 431) in a bed of sandy clay exactly like the adherent 

 portions of the formation on the lower jaw now to be described ; 

 and therefore I may assert with good reasop that my Sauro- 

 cetes must be of the same epoch and from nearly the same 

 locality. ^ 



The fragment of the lower jaw is the middle portion of the 

 whole, containing the hinder part of the two united half-jaws 

 and the beginning of the two articular branches, which are 

 broken off, as is also the whole front of the jaw. The remain- 

 ing portion, shown in PI. I. fig. 1, of half the natural size, 

 from the left side, is on this side 15 inches long and 2| inches 

 high at the highest region of the jaw, before the separation of 

 the two articular branches, but only 1| inch at the beginning, 

 under the first tooth. On the right side the articular branch 

 is broken off; but a somewhat longer portion is Avell preserved, 

 so that the whole length is 3 inches more — say 18 inches. 

 But as a piece of the jaw is wanting on this side, I could not 

 figure the right branch in its true position, and have given a 

 separate figm-e of it (fig. 4) from the outside, also of half the 

 natural size. The closed anterior ]jortion of the jaw is 11 

 inches long and 1-^ inch broad at the tip, but 2| inches at the 

 hinder part. Its transverse figm-e is an equilateral triangle 

 with outwardly curved sides and a rounded inferior edge ; the 

 interior is entirely of compact osseous substance, with only 

 two small open channels at the lower part. These two open 

 channels [canales cdveolares) are separated by a very thin 

 osseous septum (fig. 2), which, like the channels tliemselves, 

 rises much higher behind, so that each channel expands into 

 a large open cavity in the interior of the two articular branches 

 of the jaw in the same manner as in the lower jaws of the 

 Delpliinidae, to which this lower jaw seems to have been very 

 similar in construction, and especially to that of Pontojjoria as 



