HATCHER : DIPLODOCUS (mAESH) 



23 



resented in the succeeding and preceding vertebrae. ^"^ A comparison of this vertebra 

 with C 10 and C. 12, as shown in PL III. and in Figs. 7 and 8 of the text, will reveal 

 several striking differences. The zygapophyses are short and not so extended as the 

 extremities of the centrum. The anterior and posterior blades of the horizontal 

 laminae are much reduced in length, and instead of uniting to form the transverse 

 process they are widely separated and connected by a broad plate extending through- 

 out one-half the length of the vertebra and overhanging the deep, pleuro-central 

 cavity. The inferior blade of the diapophysial lamina is very short and extends 

 obliquely forward and upward, meeting the descending 

 posterior blade of the horizontal lamina at an acute angle 

 just in front of the posterior border of the pleuro-central 

 cavity, the two thus enclosing an exceedingly deep post- 

 diapophysial ca\dty. About 65 mm. (2? inches) in front of 

 the junction of the horizontal and diapophysial laminae 

 there is a large vertebrarterial canal. This opens internally 

 into the postdiapophysial cavity and externally on the outer 

 surface of the broad plate connecting the anterior and pos- 

 terior blades of the horizontal lamina. From the position 

 of this foramen it may possibly be homologous with the ver- 

 tebrarterial canal commonly found in the cervicals of the 

 mammalia. It is quite wanting on all the other cervicals in 

 Diplodocus. The posterior blade of the horizontal lamina in 

 this vertebra sends backward a rather slender process some 

 75 mm. (3 inches) in length, parallel with the external bor- 

 der of the postzygapophyses, but separated from the latter 

 by a deep, narrow groove. This groove, together with the 



vertebrarterial canal and the long, wide, deflected plate connecting the anterior and 

 posterior blades of the horizontal lamin£e are characters entirely wanting in the other 

 cervical vertebrte of this series. The pleuro-central cavity occupies most of the side 

 of the centrum. There is a vacuity in the mid-central region connecting the pleuro- 

 central cavities of the opposite sides. The bottom of the pleuro-central cavity is 

 other mse interrupted by a complicated system of oblique and intersecting lamina 

 enclosing foramina leading to the intramural cavities. The infracentral cavity is veiy 

 pronounced in this and the succeeding cer\'icals and the centra in these vertebrae are 



10 The work of freeing these vertebrpe from the matrix and restoring them was for the most part done 

 during my absence in the field. Unfortunately no drawings or photographs were taken prior to the process 

 of restoring with colored plaster. 



Fig. 8. Posterior view 

 of eleventh cervical of Dip- 

 lodocus carnegii (No. 84. Car- 

 negie Museum collections), 

 one tenth natural size. v. c, 

 vertebrarterial canal ; v. g., 

 groove on external side of 

 posterior zygapophyses. 



