4RT. 13 ANATOMY OF CHINESE FINLESS POBPOISE HOWEUL, 13 



ciated with these facets, nor upon the centra of the vertebrae posterior 

 to these. As with the remaining vertebrae of this series, the trans- 

 verse process ^ of the first thoracic has a facet for the tubercular 

 attachment of the first thoracic rib, but cranio-mediad thereto is a 

 slight bony swelling. In each transverse process of the vertebrae, 

 succeeding in caudal sequence, this swelling is larger, sharper, and 

 farther removed from the tubercular facet. They also migrate 

 gradually farther mediad and craniad until at about the ninth or 

 tenth they have assumed the position of metapophyses, and in the 

 posterior lumbar region, are situated dorsad of the neural canal. 

 Those processes, on the other hand, upon which are located the 

 tubercular facets, gradually migrate ventrad in the posterior tho- 

 racic region until by the time that the third lumbar is reached, the 

 processes, which now lack the facets for articulation with the ribs, 

 appear as arising from the centra. The transition is gradual and 

 there seems to be no reason for considering them as other than 

 diapophyses. In the anterior thoracic region, then, the transverse 

 processes represent a fusion (or lack of separation) of met- and dia- 

 pophyses, and these gradually separate to form distinct and widely 

 separated processes. If there be parapophyseal elements present, 

 these are not apparent. 



It is denied, I believe, by many embryologists that there can be 

 migration of any process from one center of ossification to another, 

 but this hypothesis needs very convincing proof. In NeoTiieris the 

 transition is gradual, there certainly appears to be such a migration, 

 and therefore in some one vertebra this lateral process must spring 

 from both of two centers of ossification, as illustrated by Flower 

 (1876, p. 53). There are often shifts in the positions of muscles, 

 and most processes are merely osteological indications of muscular 

 stresses. 



Craniad of the point at which the metapophyses become closely 

 associated with the laminae of the adjoining vertebra there are 

 fairly well developed postzygapophyses, but these disappear as proc- 

 esses farther caudad. 



The vertebra of the thoracic series whose total width measures the 

 least varies in position from the sixth to the eighth, and in breadth, 

 from 42 to 60 mm. Craniad and caudad this measurement increases. 

 The neural spines of this series, in any one individual, are all of 

 approximately equal height, that of the eighth varying from 12 to 

 21 mm. (measured from the superior border of the neural canal) 

 according to age, and possibly the sex of the individual. The spines 

 of the anterior caudal vertebrae are directed straight dorsad, while 

 both anterior and posterior to this region they are inclined some- 



* The term transverse process Is used herein merely in its physiographic sense to denote 

 the most prominent lateral process of any vertebra. 



