HATCHER : DIPLODOCUS (mARSH) 25 



they diverge again to form the superior walls of the neural canal. In this manner 

 anteriorly the left superior border of the neural canal is formed by the inferior ex- 

 tension of the right prezygapophysial lamina, and the right by the left, the inferior 

 portions of these laminae intersecting so as to form a letter X. Between the bifid 

 neural spines there is a short spinous process homologous perhaps with the single 

 spines of the posterior dorsals. This short median spine is present on the succeeding 

 cervicals and anterior dorsals. Its presence in these vertebrae has led me to believe 

 those laminse defined by Osborn as the prespinal and postspinal laminee of the bifid 

 vertebrae to be homologous with the pre- and postzygapophysial laminae of vertebrae 

 with only one spine, and I have therefore called them by the latter names. 



The Fourteenth Cervical. — This is the largest and slightly the longest vertebra in 

 the entire vertebral series. The median constriction of the centrum is the most 

 marked in the vertebral column. The pleuro- central cavities are deep, but entirely 

 separated by a median septum. The anterior zygapophyses are supported inferiorly 

 by two powerful laminae. The postzygapophysial laminae are large, and the pre- 

 zygapophj^sial much reduced. Short median neural spine. Union of rib with cen- 

 trum marked by suture. The transverse process is supported inferiorly and an- 

 teriorly by a prominent lamina which is directly opposed to the posterior blade of 

 the horizontal lamina. This is the inferior of the two anterior blades of the hori- 

 zontal lamina. It is present in the succeeding vertebrae and successively occupies 

 a more horizontal position, gradually approximating that of the superior blade. In 

 the sixth dorsal these blades are quite parallel, horizontal, and but little separated, 

 while in D. 7 and 8 they are united throughout a portion of their length, and in D. 

 9 the union is complete and the anterior blade of the horizontal lamina is quite 

 simple. See Plates III. and IV. 



The Fifteenth Cervical. — The centrum of this vertebra is some two inches shorter 

 than that of the preceding. The ball is marked b}^ a pronounced median vertical 

 groove also seen in the anterior dorsals. The superior of the anterior blades of the 

 horizontal lamina has its external surface somewhat expanded and rugose. It no 

 doubt served as a support for the muscular attachment of the heavy scapular arch. 

 The suture for the capitular attachment of the rib is well marked. There is a dis- 

 tinct but short median neural spine between the two paired spines. The principal 

 characters of the cervical vertebrae are well shown in Plates III., IV., V. 



The Dorsal Vertebrae. 

 The dorsals are distinguished from the cervicals by supporting free instead of 

 fixed ribs and in having the inferior surface of the centra regularly convex trans- 



