254 MEMOIRS OF THE CARNEGIE MUSEUM 
To recapitulate, we have brought together and arranged in making our restora- 
tion seventy-three caudals, not reckoning in this number the first modified caudal, 
which forms part of the sacrum. The vertebree from | to 12 inclusive pertained to 
specimen No. 84; from 13 to 31 inclusive and from 33 to 36 inclusive, to No. 94. 
Caudal 32 and caudals 37 to 73 inclusive belonged to specimen No. 307. 
The long whip-like prolongation of the tail of Diplodocus, the exact function of 
which is not known and can only be surmised, recalls the enormous prolongation of 
the tail which is shown in some recent reptilia. The writer has examined the skele- 
tons of a number of species of recent reptiles and finds that the number of caudal 
vertebree in Iguana tuberculata is sixty, 1n Brachylophus fasciatus sixty-five, in Poly- 
chrus marmoratus seventy, and in Varanus wiloticus from ninety-seven to one hundred. 
A comparison of the bones obtained in connection with the specimen of Cetio- 
saurus leedsi Hulke, preserved in the British Museum, indicates that they corre- 
Fic. 23. Outline drawing of a series of posterior caudal vertebrae of Cetiosaurus leedsi Hulke. (One sixth nat. size. ) 
spond approximately to the caudal vertebree 47 to 56, inclusive, in the skeleton of 
Diplodocus. ‘The bones of Cetiosaurus are relatively shorter and stouter than the 
corresponding bones in Diplodocus, but these bones both in the case of Cetiosaurus 
and of Diplodocus are remarkable because of the fact that they articulate both in 
front and behind by convex, or almost conical surfaces, showing that the posterior 
extremity of the tail possessed the very largest degree of flexibility. I am indebted 
to the courtesy of Dr. Arthur Smith Woodward for permission to give illustrations 
herewith of these vertebrae in Cetiosawrus leeds, Hulke. Fig. 23 shows an outline 
drawing made by Miss Alice Woodward, and Fig. 24 is a reproduction of a photo- 
DE Fee ROA Joe METRE) 
Fic. 24. Vertebra of posterior part of the tail of Cetivsawrus leedsi Hulke, as exhibited in the British Museum 
(Natural History). 
