140 MEMOIRS OF THE CARNEGIE MUSEUM 



The lateral canals extend from the third vertebra to the fifteenth, inclusive ; they 

 are short in any of the segments, and their posterior apertures are far larger than 

 their anterior ones. 



At the commencement of the cervical series the parial parapophyses are short and 

 not particularly well developed. They project backward from the inferior walls of 

 the lateral canals, but as the carotid canal begins to develop, these processes with- 

 draw from the former positions, move gradually lower down beneath the centrum, 

 and at the same time increase in length and importance, so that in those vertebrae 

 where the carotid canal exists, they project from its postero-inferior border directly 

 backward as parallel and not far separated spines. 



The post-zygapophyses do not appear as divergent limbs until we find them so in 

 the eighth vertebra ; in all the cervical segments anterior to this one the facets are 

 situated on the inferior aspect of the tuberous hinder end of the neural arch at its 

 lateral angles. 



Metapophyses are seen on the ninth vertebra, but gradually disappear, to be 

 entirely absent in the fourteenth or fifteenth. 



The transverse processes in the dorsal region are broad, flat, and horizontal, being 

 directed more and more to the rear as we approach the pelvis. The plates of the 

 neural spines above do not meet each other when the column is articulated, and 

 there is an entire absence of all interlacing, ossified tendons or metapophyses in this 

 region. In fact, all the vertebrae have a very clean-cut, non-angular appearance, 

 with the majority of projecting borders rounded. 



The articular ends of the centra are constructed upon the " heterocaelous " type; 

 the anterior faces in the ultimate cervicals and leading dorsals being notably wide 

 and shallow, and often riddled with foramina. 



The pygostyle and the free caudal vertebrae will be spoken of after the pelvis has 

 been described ; in the meantime we will turn our attention for a few moments to 

 the description of the sternum and pectoral arch. 



The Sternum. — This bone in the Gannets has a very peculiar form. A pectoral 

 aspect of the bone shows that the body has an oblong figure or outline, with the 

 average width nearly equal to half the length. Beyond the true sternal body the 

 anterior portion projects as a massive promontory, and a large part of the carina is 

 beyond this again. 



The anterior moiety of the bone is convex upon the dorsal side, and correspond- 

 ingly concave on the ventral aspect. Behind, the body is so flattened out in S. bas- 

 sana as to be nearly horizontal. The costal borders look outward and slightly up- 

 ward, and each usually possesses six moderately well-developed facets for the costal 



