CETACEANS. 



361 



the antero-posterior diameter of the middle one is three inches, the 

 transverse diameter of the same is one inch two hnes ; the height 

 above the alveolar process two inches and a half, the total length of the 

 tooth about four inches and a half. Later and more perfect specimens 

 demonstrate the upper part of the crown to have had its anterior 

 and posterior margins obtusely serrated. The crown is contracted 

 from side to side in the middle of its base, so as to give its transverse 

 section somewhat of the hour-glass form (PI. 90, fig. 2,) ; and 

 the opposite wide longitudinal grooves, which produce this form, 

 become deeper as the crown approaches the socket, and at length 

 meet, and divide the root of the tooth into two separate fangs. 

 The anterior teeth have a single root and are somewhat smaller 

 than the posterior ones ; the crown is sharp-pointed, conical, slightly- 

 recurved and laterally compressed, the transverse section of the 

 base forming an ellipse. The length of the anterior teeth, including 

 the root is five or six inches, and the longest diameter nearly two 

 inches. In the last discovered remains of the Zeuglodon it is stated 

 that " the enamel of the teeth is retained (1). Besides the teeth 

 implanted in the jaws as above described, there is a fragment of 

 a tooth imbedded in the matrix containing the above pieces, and 

 consisting of the base of the crown and beginning of the fangs. 

 The crown of this tooth, which is equal in size to the posterior one 

 in place, and was probably a tooth of the same jaw, is partly worn 

 down and partly broken, but is so blended with the matrix, that 

 its exact form could not be determined. Of this tooth I had a 

 transverse section made near to the base of the crown, which 

 presents the figure represented in PL 90, fig. 1, and is that form 

 which we may reasonably suppose would be characteristic of the 

 old and worn-down hinder teeth of the Zeuglodon. The crown is 

 here divided into two irregular rounded portions or lobes, placed 

 one before the other and joined by a narrow neck or isthmus. 

 The anterior lobe is the broadest, its grinding surface is sub-ovate, 

 and placed obliquely : it measures one inch three lines in the long 

 diameter, one inch in the short diameter ; the posterior lobe is 

 narrower, more regularly ovate, with the long diameter (which is 



(1) Silliman's American Journal, vol. xliv, p. 411. 



