BAROSAURUS AFFINIS. 39 
seems conclusive that they could not have belonged to the type of Barosaurus lentus, 
whose measurements, as we have seen, are rarely smaller than those of Diplodocus, 
and in the forward part of the skeleton as preserved largely exceed it. D. longus and 
D. camegiei are approximately of a size, nor is it clear that they are specifically 
distinct. 
Metacarpal I (PL VI, Fig. 9). — This bone. is absolutely perfect, and while slightly 
fissured, has been naturally cemented so that no repair was necessary. In form it 
resembles that of Morosaurus lentus very closely, the likeness being much greater than 
to Diplodocus longus. The main distinction from Morosaurus lies in the outer and 
distal aspects, the latter being wider transversely and of less antero-posterior extent, 
while the outer posterior angle is prolonged outward. The articular face in Morosaurus 
therefore is roughly rectangular, although with an inwardly curved posterior border, 
while in Barosaurus the outer and inner sides form an angle of nearly 45 degrees 
with each other. This of course renders the form of the outer surface somewhat 
different as well. 
Metacarpal II (PL VI, Fig. 10). — This is only partly preserved, as the distal half 
is gone. In size it once more approximates that of Morosaurus lentus, but differs in 
that the proximal articular face is more rugose, as though it bore a relatively somewhat 
thicker articular cartilage. The surface of the bone in Barosaurus is almost convoluted, 
in Morosaurus pitted. There is a similar distinction in the equivalent surfaces of 
metacarpal I, but it is somewhat less marked in the former. In Barosaurus the shaft 
is much more irregular in section, with one acute angle, while in Morosaurus it is again 
roughly rectangular. 
Measurements of the Metacarpals 
Barosaurus Morosaurus Diplodocus 
ajfflnis lentus longus 
mm. mm. mm. 
Metacarpal I 
Length 138 137 209* 
Proximal face, transverse diameter 86 92 146 
" anterior-posterior diameter 105 io6f 148 
Distal face, transverse diameter 120 105 152 
" " anterior-posterior diameter 69 76 105 
Width of shaft (least) 80 79 108 
Metacarpal II 
Length 179 
Proximal face, transverse diameter 97 96 
" anterior-posterior diameter 98 112 
* From Marsh's figure, 
t Slightly restored. 
