144 FIELD COLUMBIAN MusEUM—GEOLOGY, VOL. II. 
Fig. 3). It resembles that of /Vyctosaurus, though having a less elon- 
gated process beyond the articular lateral emargination. The figures of 
the carpal bones of Orntthochetrus given by Seeley (Ann. Mag. Nat. Hist. 
Aug. 1870, and Dragons of the Air, p. 124) closely resemble these bones. 
Professor Seeley says of the ‘lateral carpal’’: ‘It is a flat, oblong bone, 
attached to the inner side of the distal carpal, and, instead of being pro- 
* 
longed distally in the same direction as the other metacarpal bones, is - 
turned round and directed upward, so that its upper edge is flush with the 
base of the radius, and gives attachment to the pteroid.” I had supposed 
that the larger end, as shown in the present figure, fitted into the interval 
between the two carpals, and that the emargination was for the articulation 
of the rounded head of the pteroid, though perhaps the position assigned 
to it by Seeley is the correct one. The bone is thin on the sides shown in 
the figure, so that the articulation of the pteroid must have been either in 
the emargination or with the broader end. Marsh says* that it “‘stands 
nearly at right angles with the wrist,’’ and I am inclined to think he was 
right. The structure of these wrist bones is almost identical with what it 
is in Preranodon. 
MEASUREMENTS OF CARPAL BONES. 
mm 
Length of articulated carpus—..-... 2/J2022_ 2. oe ee 
Greatest diameter of distal carpal... (2.202 Ce ee 24 
Lesser diameter of sdmeést-~2 2 2253000 5 ee a 14 
Greatest diameter of- proximal carpal... 22-2502 oe 26 
Length of:“ lateral carpal "\i.--- 2.22 522 ee ee 17 
Width of same-.-5 202222 0 Soak ea ee See 8 
Metacarpals. The first metacarpal, or pteroid (Pl. XLII, Figs. 4, 5), 
is an elongated, pointed, styliform bone, with an enlarged articular car- 
pal extremity. In both arms this bone has been displaced, though so 
closely associated with the corresponding extremity that the position is 
assured. Its articular end is broad, its margin nearly at right angles with 
the long axis of the bone. The articular surface is nearly at right angles 
with the transverse diameter, in life nearly circular in outline, and decid- 
edly convex. It is separated from the bone by a slight constriction. 
The dorsal border of the bone is very gently concave throughout, and 
the inferior border is correspondingly convex for the greater part of its 
extent. The pteroid of the right arm is lying close to the lateral carpal, 
as though its articular surface fitted into the lateral emargination of that 
bone in life. Oscar Fraas was the first, so far as I can learn, to recognize 
the real nature of this bone as belonging to the first digit,7 a view after- 
wards adopted by Marsh and Zittel. 
*Amer. Journ. Sci., 1882, p. 255. 
+Paleontographica, 1878, p. 170. 
