ART. 27 A FOSSIL PHYSETEROID CETACEAN KELLOGG 5 



The extremities of the mandibles are relatively large in comparison 

 to the rostrum and in general conformation are somewhat similar to 

 those of Physeter, Pressure or other factors resulted in the separa- 

 tion of the mandibles at the symphysis. The left mandible does not 

 lie in its normal position and its inner face is appressed against the 

 ventral surface of the rostrum. The proximal portions of the mandi- 

 bles were not collected and as the inner faces of these mandibles begin 

 to diverge some 170 mm. in front of the point where they were broken 

 off, it is evident that all of the symphysial region is represented. If 

 this is the case then the symphysis of the mandible is coextensive 

 with the first eight pail's of teeth. Both mandibles curved upward 

 from the posterior end of the symphysis forward. The distal ex- 

 tremity of each mandible is obliquely truncated in a dorso-ventral 

 direction while the external and internal faces of the mandible de- 

 scend abruptly from the dorsal surface which is relatively flat. 



The tooth-bearing portion of the mandible is relatively massive 

 and the bone itself is rather dense. The alveoli (pi. 2) are large and 

 the posterior ones occupy more than half of the width of the mandible. 

 In this fossil, the series of teeth in each mandible consists of more 

 than eleven slightly curved and conical teeth. The first and third 

 teeth are the smallest of the mandibular series. The roots of all the 

 teeth available for examination from the upper jaw are terminated 

 obtusely and no doubt those of the mandible are similar in appear- 

 fince. Two teeth, the inner one much smaller than all of the follow- 

 ing with the exception of the third, project obliquely forward from 

 the extremity of each mandible. 



Teeth. — Turning to the teeth, we find that they are all very large 

 and that some of them may have projected 4 or 5 inches beyond 

 the jaws. They are separated by intervals or septa narrower than 

 the thicloiess of the cement. In respect to their mode of implanta- 

 tion in the jaw, the teeth differ froili those of Physeter in that they 

 are lodged in distinct alveoli and the septa extend the full depth 

 of the alveolus. These alveoli are too large to hold the teeth in 

 place independently^ of a dense ligamentous gum which accounts 

 for their absence from the alveoli in the upper jaw. The position 

 of the mandibles prevented the teeth from falling out of the alveoli 

 and in some instances the matrix in the alveolus which encircles 

 the root attains a width of 20 mm. or more. This interval affords 

 another indication of how loosely the teeth were implanted in the 

 jaws. All the crowns of the teeth, with the exception of the third 

 in the right mandible, either were broken off at the time the speci- 

 men was removed from the sea cliff or were destroyed before burial. 

 The summit of the crown of this tooth is abraded and the enamel 

 is ornamented with coarse lono^itudinal striae. 



