214 ME. W. P. PYCRAFT ON THE MOEPHOLOGY AND 



The pre-sacrals resemble those of Dromcens and Casuarius in that they descend 

 below the level of the ventral border of the pre-ilium, but not greatly so. In Struthio 

 this feature is much more marked, the whole centrum and base of the neural spine 

 beino- exposed in side view. The parapophysial processes of the first caudal are 

 directed backwards instead of forwards. From this cause the true sacral vertebrae 

 are completely isolated. 



In Struthio, Casuarius, Dromceus, and Apteryx, it will be remembered, the para 

 pophysial process of the first or even first and second caudals may combine with 

 those of the true sacrals to form a sacral mass, the true nature of which is difficult 

 to make out in the adult. The post-sacrals (caudals) resemble those of Struthio 

 rather than any other Ratitce in the great development of the diapophysial process, 

 which extends upwards, outwards, and backwards to separate the post-acetabular 

 ilium. 



In Dinomis, however, this separation of the post-acetabular ilia is carried to a 

 greater length than in any other Eatite. The neural spines of the Dinornithidce are 

 peculiar in that they combine dorsally to form a broad lozenge-shaped superficial plate 

 of bone which serves as a cover to the huge fossa that otherwise exists between the 

 upwardly directed transverse processes and the post-ilia. 



The synsacrum of the Crypturi differs from that of all the other forms herein 

 described. Moreover, in the points wherein it differs from these it resembles the 

 Neognathce. 



One of the most noticeable differences is the fact that the post-sacrals have lost their 

 neural spines. In all the flightless Palceognathw these are of great length. The 

 diapophyses of the post-sacral region rise from the top of the centrum, at the base of 

 a long, faint, median ridge marking the position of the neural spines in other forms. 

 These diapophyses develop thin plates of bone which fuse one with another to form a 

 lozenge-shaped plate, protecting the inter-diapophysial fossae, as is done by the similar 

 plate from the neural spines in Dinomis. 



The synsacrum of the Tinamous includes one thoracic, four lumbar, five lumbo-sacral, 

 and five post-sacral. There are no parapophysial processes abutting against the 

 pectineal process as in the flightless Palceognatlm. This process, it should be 

 mentioned, has shifted further backward relatively to the sacral vertebrae, so that a 

 line drawn across from the base of the anterior concave border of the one would pass 

 immediately in front of the first sacral. 



The sacral ribs are very long, and articulate with the ilium immediately behind the 

 acetabulum by a long vertical roughened surface. The rib of the second sacral is 

 vestigial or wanting. 



The free caudal vertebrae in the Palceognathw do not exceed ten in number. Some- 

 times the 9th and 10th are more or less fused. 



In Struthio the 10th is laterally compressed to form a kind of pygostyle. 



