FOSSIL GENUS BASILOSAURUS. 13 



the two meeting in a sharp angle within and above the longitudinal median line of 

 the lower surface, which is well exhibited in the sections, (PL III., figs. 3 and 4,) 

 posterior to the insertion of a canine tooth. The latter specimen, (fig. 4,) upon a 

 careful comparison with^ that of Prof. Warren, I am satisfied is identical with it. 

 From Prof Emmons's description I was disposed to consider them different; but he 

 was mistaken in describing the anterior portions of the lower maxilla as being united, 

 and having a groove or sulcus ; whereas they are only united at the terminal extremities 

 "of the rami anteriorly ; the interspace being filled with the matrix, which requires to be 

 closely scrutinized to show the fact. I pointed it out to Prof. Wyraan when we lately 

 examined the specimen together. A little above the longitudinal median line on the 

 inner face, the inner alveolar process arises like a continuous parapet, of a half-inch in 

 thickness, extending nearly as much above the insertion of the canine tooth (PI. III., 

 fig 5, a,) which is placed almost perpendicularly in the alveolus. In this respect it is 

 directly the opposite of the Megalosaurus, where the external edge of the jaw rises almost 

 an inch above the margin, forming a lateral buttress to support the teeth externally. 

 Immediately anterior and posterior to this canine, are hollow pits or depressions on 

 the outer surface of the jaw for the overlapping of the tusks of the upper jaw. In 

 Prof Warren's specimen, this inner thick plate or buttress is distinctly marked, but 

 Dr. Emmons's figure does not represent it. In my first specimen there is no such 

 additional plate, or projecting alveolar process, on the inner side of the maxilla. In 

 the latter case, the pits, of which two exist in each lateral fragment, certainly show an 

 approximation in the animal to the Saurian rather than to the Cetacean type. Both 

 are hollow. 



" In all the genera of Crocodilians," observes Prof Owen, in his Odontography, "the 

 teeth of the upper and lower jaws are so placed that their points, instead of meeting, 

 interlock. In the Crocodiles, (genus Crocodilas,) the first tooth in the lower jaw 

 is received into a notch excavated in the side of the alveolar border of the upper jaw, 

 and is visible externally when the mouth is closed." "In the Gavials, (genus 

 Gavmlis,) the first as well as the fourth tooth in the lower jaw, passes into a groove in 

 the margin of the upper jaw, when the mouth is closed." p. 286, 



I have not yet seen a perfect upper maxilla, but supposing from the form of the 

 groove that a similar tusk existed in the upper jaw, here would be another approach 

 to the Gavials, (so far as the canines are concerned,) since their teeth are nearly equal in 

 size and form in both jaws. In the figures given by Faujas de St. Fond of the Asiatic 

 and African crocodiles, these pits or depressions in the lower jaw are obvious cha- 

 racters. 



Of the caudal vertebra I received twelve, six krger (PI. II., figs. 6 and 7) desti- 

 tute of spinous processes, and six smaller (PI. II., figs. 4 and 5) without any pro- 

 cesses — merely rudimentary notches. The largest of the former is three and a half 

 inches lono-, and four inches in the width of the articular surfaces, which are circular 



