( 191 ) 



The zygomatic process well developed. 



Rostrum dilated towards its anterior end, compressed and earinate beneath the 

 large prespheuoid fossae. 



Mandible very slender ; posterior angular process small. 

 The dimensions of the skull are : — 



Total length .. . 



Length of crauio-facial axis . 



„ „ basis cranii . 



„ ,, roof . . . . 



Width at paroccipital processes 



„ „ s([uamosal prominences . 



„ „ temporal fossae 



„ ,, postorbital processes 



„ „ preorbital processes 

 Distance between temporal ridges . 

 Height of cranium 

 Width of tymijanic cavity 



„ „ temporal fossae 



„ „ orbit . . . . 



Distance between optic foramina . 

 Length of premaxilla 



„ „ body of premaxillae 

 Width 



122 mm. 

 97 

 30 

 76 

 55 

 G5 

 45 

 73 

 47 



42 

 20 

 26 

 32 

 10 

 66 

 27 

 25 



The above measurements are taken according to the rules laid down by Prof 

 Jeffrey Parker in his paper on the Cranial Osteology of the Di'iwrnithidae {Trans. 

 Zool. Soc. Vol. XIIL 1895, p. 373). 



The Vertebral Column. — There are twenty-one true cervicals, two cervico-dorsals, 

 and four free dorsals. The two halves of the neural spine of the atlas are imperfectly 

 united, their anterior two-thirds being separated by a narrow vertical cleft. The 

 neural spine of the axis is not very prominent, and its posterior face bears a deep pit 

 for the insertion of a ligament. The neural spines of the cervicals 3, 4, and 5 are 

 bifid ; in the sixth the bifid spine is represented by two tuberosities, which in the 

 succeeding vertebrae diverge from one another and become reduced in height, till on 

 17 we have two low tuberosities, separated by a considerable interval and arising from 

 a common transverse ridge. In 18 and 19 these tuberosities become more prominent 

 and again ajiproach one another, while in 20 we have a high median spine which 

 .slopes forward and still shows traces of the bifid condition in the slight forking at its 

 posterior upper angle. In 21 — 25 the neural spine continues to increase in breadth 

 and height, but in the last two free dorsals, although the increase in height is main- 

 tained, the spine becomes very narrow from before baekvrards. 



The centrum of the axis bears a median haemapophysis, as also does that of the 

 third; in the fourth this process is only slightly indicated. The fifth vertebra was 

 missing and has been restored in plaster. In the sixth the ventral surface is deeply 

 concave from side to side, and the paired catapophyses begin to appear ; these 

 increase in height to the sixteenth, in the seventeenth they are reduced, and in the 

 eighteenth replaced by a median haemapophysis. This increases in height and .antero- 

 posterior extent to the twenty-fourth ; on the twenty-fifth there is a median haema- 

 pophysis at the anterior border of the centrum, and a pair of blunt processes near the 



