46 FIELD COLUMBIAN MusEuM—-GEOLOoGY, VOL. II. 
the emargination behind represents a distinct foramen in the com- 
pleted girdle—the interclavicular foramen, of which the only mention 
hitherto that I can find is by Seeley (Proc. Roy. Soc. Lond. li, p. 140), 
whose figures I reproduce here. 
In Pl. XV is shown the articulated pectoral girdle from below, 
and in Pl. XIV, the same is shown in front view. As a whole, 
the girdle forms a rather deep trough, with the dorsal rami of the 
scapula directed upward and somewhat outward. Its exact position 
in relation to the ribs is difficult to state, but I do not think that the 
position given-in the restoration can be far wrong. The slight 


ae | a 
/ f | 
/ 
4 ease 
| he 
MBE cx r 
eee \ 
tas 
‘ Tiel oe s 
fp Oe aes, ‘ i 
NY “ 
1 
co. 
CHS the ts 
‘ : 
Scapulo-clavicular girdle of Plesiosaurus mudgei from above; the missing parts restored in 
dotted lines. /c., episternum; c/., clavicle; sc., scapula; co., epicoracoid process. ‘ 
degree of curvature of the ribs in the pectoral region must have left a 
rather angular margin to the thorax on either side, filled in, in part at — 
least, by the cartilaginous continuation of the thoracic ribs, which 
the preserved ends plainly. show were present. The upper surface of 
the girdle was not hollowed much, if any, longitudinally, so that the 
base of the neck must have been in life quite deep. 
An examination of the under surface of the girdle, as shown in 
Pl. XV, furnishes, I think, convincing proof that the space between 
the scapula, epicoracoid process and the elliptical lines on the ven- 
tral surface of the episternum was filled in in life by cartilage, join- 
ing the coracoid and scapula and covering the squamous portion of 
the episternum, but leaving the interclavicular foramen free. Ossifi- 
