May 25, 1900.] 



SGIENCE. 



817 



the hillside, on which the discovery was 

 made, will result in the discovery of some 

 additional portions of the skeleton. 



It is not the intention of the writer in these 

 lines to enter into a description or discussion 

 of these exceedingly interesting and impor- 

 tant remains, save for the purpose of calling 

 attention to the fact that the specimen 

 under consideration appears to throw light 

 upon the hitherto unsettled number of the 

 dorsal vertebrae in the Sauropoda. Profes- 

 sor Marsh has figured the number of dor- 

 sals in Brontosaurus as fourteen. Professor 

 Osborn in his memoir says " We may pro- 

 visionally adopt 15 as the number in Diplo- 

 docus." The specimen obtained by the 

 Carnegie Museum shows but ten dorsal 

 vertebrae. These vertebrae were found in 

 regular order from the sacrum forward. 

 The six posterior presacral vertebrae inter- 

 locked by their zygapophyses. The sev- 

 enth and eighth presacrals articulated with 

 each other, but were displaced vertically, 

 having been depressed in the mud, which 

 subsequently solidified to form the matrix. 

 The ninth and tenth were also interlocked, 

 and no gap existed between the eighth 

 and ninth except that produced by the de- 

 pression already noted. The first cervical 

 lying in front of the tenth presacral was 

 displaced at an angle from the axial line of 

 the skeleton, but if restored to a normal 

 position the gap between it and the most 

 anterior of the dorsals would have been 

 filled, and, now that' these vertebrae have 

 been freed from the matrix, they are found 

 to closely articulate. The cervicals were 

 for the most part interarticulated, all lying 

 in such position as to show the serial 

 order.* 



*I am indebted to Mr. A. S. Coggeshall, the Chief 

 Preparator in the Department ofj Vertebrate Paleon- 

 tology in the Carnegie Museum, for the statements 

 given above as to the exact location in situ of the 

 vertebrae. Mr. Coggeshall preserved accurate memo- 

 randa of locations in the field-notes, which he made 

 while assisting in the exhumation of the remains. 



From the foregoing facts it appears that 

 the number of dorsal vertebrae in Diplodocus 

 is only ten. 



A further confirmation of this view is de- 

 rived from the number of ribs which were 

 discovered. Beginning with the dorsal 

 vertebrae immediately before the sacrum 

 we find the short posterior ribs as deline- 

 ated by Professor Osborn, followed, as we 

 advance, by ribs rapidly increasing in 

 length, until we find attached to the seventh 

 presacral a rib five feet eight and a half 

 inches in length. This represents the 

 maximum development in the length of the 

 ribs. Both ribs of the seventh presacral 

 have been recovered. We have not found 

 time as yet to carefully adjust the ribs to 

 the vertebrae, but we have every reason to 

 think that we have recovered all of them 

 except two. Twenty is then the number of 

 the dorsal ribs in Diplodocus and the infer- 

 ence is plain that there must have been but 

 ten dorsal vertebrae. 



The correspondence between the struc- 

 tures of the sacral region in Diplodocus and 

 those found in the struthionid birds has 

 already been pointed out by Professor Os- 

 born. I may say that this likeness is 

 further shown in the number of the dorsal 

 vertebrae, and the conformation of the 

 scapular girdle, as well as in certain features 

 of the cervical vertebrae. These colossal 

 reptilia reveal in portions of their osseous 

 framework marked tendencies in the direc- 

 tion of a development along avian lines. 



f Eleven are found in the 

 specimen at the Carnegie 



I Museum, atlas and axis be- 



I ing as yet undiscovered. 



I There may have been more 



Cervicals at least 13 -J than thirteen cervicals, 



though their great length, 

 averaging two feet, seems 

 to militate against the ex- 

 istence of many more than 



L the number given. 



Dorsals 10 



Sacrals 4 



Caudals 32-35 (Osborn) 



f Both specimens agree in 

 \ showing only four sacrals. 



