604. PROF. H. G. SEELEY ON THE DINOSAURIA OF 
size or form of the articular face. When placed together, end to 
end, without allowance for intervertebral cartilages, the series of 
dorsal vertebrae measures 19 inches; but this does not represent the 
entire length of the dorsal region, because at least one vertebra is 
missing between the last dorsal and first sacral, and at least one 
between the first dorsal and last cervical. 
Neural Arch.—The most perfect specimen of a dorsal neural arch 
is figured (Pl. XXXYV. fig. 14). It measures 14+ inch from the 
sutural surface uniting with the centrum, to the slight transverse plat- 
form (a) from which the compressed neural spine (¢) rose; though now 
broken away, the platform was horizontal, small, convex from front 
to back, concave from side to side, with the outer prolongation 
notched out posteriorly and directed a little upward. Its anterior 
border reaches no further forward than the middle of the neuro- 
central suture. There is the usual strong buttress below this trans- 
verse process, compressed from side to side, and terminating in an 
elevated vertically ovate articulation for the rib (6), looking outward 
and a little upward, ;%, inch wide and ;°; inch long, above which 
the buttress is constricted, and below which it widens and disappears. 
The prezygapophyses are broken away (@) ; but the posterior zygapo- 
physes (c) are flat ovate facets looking obliquely downward and out- 
ward, converging inferiorly so as almost to unite, but remaining 
separated by a groove. The arch over the neural canal is remark- 
ably high and narrow. 
Dorsal Ribs.—The dorsal ribs are represented by a number of 
fragments, but none are sufficiently perfect to give any idea of their 
length. The fragments are all more or less curved. The two spe- 
cimens figured (Pl. XXXYV. figs. 11, 13, 12) give some idea of the 
difference in size of the specimens and of the typical characters 
which they present. They are especially remarkable for having the 
under or visceral surface compressed and the dorsal surface expanded 
like the crosspiece of a capital T. This would suggest a great 
development of intercostal muscles, and would have led me to anti- 
cipate for the animal some form of dermal armour ; but since no 
trace of armour was found with the remains, the explanation of - 
this form of rib has yet to be discovered. 
Sacral Vertebra (Pl. XXXIV. fig. 3)—The sacral vertebra, as 
preserved, are six in number, and the series is apparently complete ; 
but they do not become anchylosed into a sacrum, though the arti- 
cular surfaces were evidently in intimate juxtaposition. It is im- 
possible to affirm that this condition is proof of the immaturity of the 
individual, though such a conclusion is natural. As placed together, 
end to end, the series of vertebrae measures 83 inches in length. As 
in the other regions of the vertebral column, there is no trace pre- 
served either of neural arches or of the short sacral ribs in union with 
the centrums, except the impressed surfaces for their articulation 
upon the sides of the centrums. In the absence of the usual aids 
for determining the order of succession of the bones, I have arranged 
them in sequence by means of the form of the neural canal and the 
mutual adaptation of the articular surfaces. Like the sacral ver- 
