TRUE : THE FOSSIL CETACEAN, DORUDON SERRATUS. 75 



the ramus and a very small part of the symphysis (Plate 2, figure 6), 

 with a canine, or incisor, tooth in position. This latter piece was figured 

 in 1847 by Gibbes in his Plate 3, figure 2. Nearly all of it, however, 

 has been lost since that date, and the tooth has been detached but is 

 still preserved. 



The left side of the mandible (Plate 3, figure 1) was also figured by 

 Gibbes in 1S47 in his Plate 3, figure 1. All the parts there shown are 

 preserved, except the portion of a crown of a tooth which appears near 

 the left-hand end of the figure. This figure is one-half natural size. 

 Whether this mandible belongs to the same individual as the cranial 

 fragments is uncertain, but if the proportions of the restoration are 

 correct, it was about 680 mm. long when complete, or about one-half 

 longer than at present. The first two-rooted tooth, or premolai - , appears 

 to be the one of which a portion of the crown is shown in Gibbes's figure. 

 This is situated 104 mm. behind the anterior end of the jaw. In front 

 of it, at the anterior end, are a portion of a simple alveolus, which should 

 be that of the second incisor, and two other simple alveoli about 24 mm. 

 in diameter, which should represent the canine and third incisor. These 

 are 15 mm. apart, and the latter is 15 mm. from the first premolar. The 

 latter tooth is succeeded by the second premolar, apparently without an 

 interval. The upper end of the roots of the tooth measures 39 mm. 

 antero-posteriorly. The location and number of teeth posterior to the 

 second premolar cannot be determined from the specimen. 



The symphysis is about 152 mm. long, as indicated by the flat internal 

 surface of the left side of the jaw, and was probably but little prolonged 

 anteriorly when complete. It ends posteriorly about opposite the second 

 premolar, as in Prozeuglodon. 



Of the atlas which accompanies the skull-fragments, little more than 

 the low r er half remains (Plate 2, figure 13). It is comparatively slender. 

 The anterior articular facets are strongly declined. They are separated 

 from the posterior facets by a ridge. The posterior facets are oblique 

 rather than vertical. The inferior lateral process (broken) is thick at 

 the base and compressed. It is only moderately directed downward and 

 backward. The vertebrarterial foramen is large and is in line with the 

 outer margin of the anterior articular facet. The following measure- 

 ments were taken from the fragment : — Breadth between outer margins 

 of anterior articular facets, 104 mm. ; greatest thickness of atlas, 33 ; 

 least thickness in median line, 24 ; breadth of inferior transverse process 

 at base, 25. 



The teeth figured by Gibbes in 1847 in Plate 2, figure 1 (two views), 



