HOLLAND : THE OSTEOLOGY OF DIPLODOCUS MARSH 251 
Fig. 3. ‘This bone, the original of which was critically examined both by Mr. Hatcher 
and by the writer, is undoubtedly one of the cervical vertebree of a Brontosaurus and 
not of a Diplodocus. The bones which were obtained by Professor Marsh in many 
cases came from what we are in the habit of calling “ general quarries,” that is, from 
deposits in which the bones of a number of individuals, sometimes representing dif- 
ferent genera, are found commingled. The recovery by the Carnegie Museum in 
1899 of the entire series of the cervical vertebree of Diplodocus, most of them articu- 
lated and in the position held in the living animal has made the whole subject clear 
and any one at all familiar with the matter may easily verify for himself the cor- 
rectness of the statement that Professor Marsh was in error in this particular instance. 
The fact that Professor Marsh had attributed one of the cervical vertebree of Bronto- 
saurus to Diplodocus had not been detected by Mr. Hatcher at the time that he 
prepared his first Memoir upon Diplodocus, but in Vol. II. of the Memoirs of the 
Carnegie Museum, p. 75, he points out the error into which Professor Marsh had 
fallen and calls attention to the fact that the comparison he made on p. 56 of his 
Memoir, between the cervical vertebrae of Diplodocus carnegiei and the cervical ver- 
tebree attributed by Professor Marsh to Diplodocus longus is without value. 
The cervical vertebrae belonging to the series after the axis have been so thor- 
oughly and accurately described by Mr. Hatcher that it would be a work of superero- 
gation for the writer to say anything in addition to what he has already so well said. 
THe Dorsal VERTEBRA. 
In a paper published by the writer in Science, N. 8., Vol. XI., p. 816, it was 
stated that the number of dorsals ascertained to have belonged to specimen No. 84 
(Carnegie Museum Catalogue of Vertebrate Fossils) was ten. At the time that this 
paper was written the vertebree which are codssified and united with the ilia had not 
yet been freed from the matrix, and the fact that the anterior vertebra belonging to 
the five which are codssified in the sacral region might, as has been pointed out by 
Mr. Hatcher, be reckoned as a modified dorsal rather than as a true sacral, had been 
overlooked. Mr. Hatcher makes the first of the bones coéssified in the sacral region 
the eleventh dorsal. He has, however, very aptly pointed out (Memoirs of the Car- 
negie Museum, Vol. I., p. 30) that it is a matter of individual opinion as to whether 
this bone should be reckoned as a sacral or as a dorsal. This vertebra marks the 
transition from the dorsals to the sacrals, and, as has been pointed out by Mr. 
Hatcher, “functions as a sacral.” The number of vertebrae in Diplodocus to be 
reckoned as belonging to the dorsal series depends altogether upon the view which 
is taken of the composition of the sacrum. If the vertebrae which codssify in the 
