788 THE AMERICAN NATURALIST. [Vor. XXXIV. 
border of the ilium, both in Diplodocus and Apteryx ; the last 
dorsal vertebra of Diplodocus coalesces with the superior . 
border of the ilium by a bar, which may be considered either 
a metamorphosed rib or an expansion of the metapophysial 
lamina : if this is a rib, Diplodocus presents a condition analo- 
gous to that in Struthio, in which the last vertebra and rib, 
technically known as a * pelvic vertebra," is all but united 
with the ilium. (See Figs. 8 and 9.) 
Dorsal Vertebral Formula. — 'The latest contribution to this 
subject results from the explorations of 1899 in the dinosaur 
beds of Wyoming. Holland (1900, 
p. 817) shows from the explorations of 
Fio: 7. deu RAINS aL Posterior cervical, lack 
After Marsh. 
rasaurus. Anterior dorsal vertebra, with blunt | median spine. After Cope. 
the Carnegie Museum in the Jurassic of Wyoming that the 
number of dorsal vertebrae in Diplodocus has been overestimated 
hitherto by Osborn; that this animal possesses in fact only 
ten dorsal vertebra, the entire vertebral formula being esti- 
mated as follows: 
Cervia. . . . . at bs 13 
DOM = - |. IO 
BAUW o e 4 
kudas 2... s 32-35 
Contemporaneous with this discovery is that of the American 
Museum party, that the dorsal vertebrae of Morosaurus also 
number zen. 
