22 E. C. CASE 



of the rib ; it is probable that the main portion of the capitulum 

 was attached to the intercentrum, but we have here the first step 

 in the formation of the type of articulation which is present in 

 all posterior vertebrae. In other respects the vertebra resembles 

 those immediately preceding it ; the neural arch is attached to 

 the centrum, but the sutural connection is very distinct. 

 Attached to the spine of this vertebra is one of the intercentra 

 such as is found in the posterior portion of the column. It is 

 broadly crescentic, with but slight curvature, and is of consider- 

 able antero-posterior extent on the mid-line. The bone is very 

 thin, and there are no faces for the capitulum of the rib ; it is 

 probable that the intercentrum is displaced and belongs farther 

 back in the series. One thing seems very certain : the width of 

 these intercentra is too great to permit their having occupied a 

 position between the vertebrae in the anterior portion of the col- 

 umn, and there are no articular faces for them on the lower 

 portion of the anterior face of the centrum. They must have 

 rather underlain the point of union of the two vertebrae. 



MEASUREMENTS OF THE TWENTY-FOURTH VERTEBRA, 



Length along bottom line of centrum ----- 0.0285"! 

 Length intercentrum attached to spine - . . - 0.032 

 Width of the intercentrum antero-posterior . - - - 0.009 



Beginning with the twenty-fifth, the series is complete and in 

 position to the second caudal, so that it is certainly the seventh 

 presacral. 



The twe^ity -fifth, seventh presacral vertebra (Fig. 18), has the 

 articular face for the capitular portion of the rib well developed, 

 and the posterior edge of the face is supported by a strong 

 protuberance from the side of the centrum. 



Length along the bottom line of the centrum - - . 0.027" 



In the twejity- sixth, sixth presacral (Fig. 18), the base of 

 the rib is still attached to the vertebra and shows clearly the 

 change in the manner of articulation. The tuberculum is 

 attached to a very short transverse process extending from the 

 side of the neural arch and the capitulum to the articular face 

 formed on the edge of the anterior face of the centrum. The 

 articular face is quite large and stands out prominently from the 



