November 30, 1900.] 



SCIENCE. 



829 



anterior to the 3 sacral vertebrse with coa- 

 lesced spines as a dorsal rather than a sa- 

 cral. I also assume that we have repre- 

 sented in our skeleton the complete dorsal 

 series, but of this we cannot be absolutely 

 certain, since the vertebrae were not found 

 in an articulated series. Unfortunately no 

 diagram was made, at the time of exhum- 

 ing the remains, showing the relative posi- 

 tion of each of the vertebrse in the quarry. 

 Early last spring, at the request of the 

 writer, Mr. W. H. Reed (who assisted in 

 unearthing the skeleton) , while again on 

 the ground, made a diagram of the quarry, 

 showing the relative positions, as he re- 

 membered them, of the various bones of 

 the skeleton. This diagram shows two 

 rather marked breaks in the vertebral col- 

 umn, and I may add that a close examina- 

 tion of the dorsal series as now mounted 

 seems to indicate that there are two or 

 more missing vertebrse. This is especially 

 noticeable between presacrals 7 and 8 or 

 dorsals 5 and 4. In presacral 7, the capit- 

 ular facet is situated well up, on the side of 

 the neural arch, while in the presacral im- 

 mediately anterior it extends well down on 

 the centrum. Not only does this sudden 

 shifting of the position of this articular sur- 

 face seem to indicate that there are wanting 

 at this point in the series one or more ver- 

 tebrse, but I may add that according to 

 Professor Osborn's figures the actual posi- 

 tion of the capitular facet on presacral 8 is 

 much higher than that occupied by that 

 facet on the vertebra that has been as- 

 signed to the same position in our series, 

 thus indicating a more anterior position for 

 this vertebra, and consequently a greater 

 number of dorsal vertebrae than has been 

 given above. Since the vertebrse in the 

 American Museum series were all found 

 interarticulated by their zygapophyses, 

 there can be no question of the position of 

 each dorsal in that series, relative to the 

 sacrum. There also appears to be a break 



in our series between the last cervical and 

 the first dorsal, and it is barely possible 

 that the first true dorsal or last cervical is 

 wanting in our series. From the above it 

 will be seen that there is a possibility that 

 when the actual number of dorsal verte- 

 brse in Diplodocus is definitely known, it 

 will be somewhat greater than that given 

 here, and that Professor Marsh was per- 

 haps not far wrong when he figured it at 14. 



Should the first vertebra anterior to the 

 three sacral vertebrse with coalesced spines 

 come eventually to be considered as a sa- 

 cral, rather than a dorsal, the sacrum would 

 then have to be considered as composed 

 of 5 vertebrse instead of 4, as has been 

 done by Osborn, Holland and the present 

 writer. If we consider this vertebra as a 

 modified dorsal and not a sacral, there would 

 seem to be no good reason why we should 

 not consider the fourth sacral, which also 

 has a free spine, as a modified caudal, since 

 the centra of each are firmly ankylosed 

 with the sacrals bearing coossified spines. 

 This interpretation would reduce the num- 

 ber of true sacrals to 3, as was originally 

 given by Marsh. 



Another marked character brought out 

 by our skeleton is the great absolute and 

 proportionate length of the cervical region 

 in Diplodocus. Osborn has given the known 

 and estimated lengths of the vertebral col- 

 umn as follows : 



Caudals, 30 feet. 



Sacrals, 2 feet. 



Dorsals (estimated) 12 feet. 



Cervloals (estimated) 12 feet. 



Skull, 2 feet. 



The length of the cervical series alone in 

 our skeleton is somewhat over 21 feet; and 

 the atlas is yet to be found. The dorsal 

 series is somewhat shorter than that esti- 

 mated by Osborn. 



The main points that it is desired to em- 

 phasize are : 



1. The number of cervical vertebrse in 

 Diplodocus is definitely fixed at at least 15. 



