SINCLAIR : TYPOTHERIA OF THE SANTA CRUZ BEDS. 
25 
posterior margins of the centrum. The distal caudals are mere cylinders, 
without neural arch or transverse process. 
The ribs (text fig. 9) are slender, with little tendency toward flattening, 
even in the anterior members of the series. Distally, near the junction 
with the costal cartilage, the rib shaft expands slightly. The costal carti- 
lages were calcified and are preserved in No. 15,352 (text fig. 9, B). 
Fig. 9. 
A, Protypotherium sp. Posterior cervicals and anterior dorsals with ribs in place, viewed from 
the left side, x f (No. 15,352). B, the same from below, showing the sternum and calcified 
costal cartilages, x f . 
The sternum consists of six pieces, of which four are mesosternal. The 
first sternal segment (figured separately in PI. VI, fig. 7) is strongly 
keeled interiorly in P. australe , but this keel is wanting in No. 15,352. 
The mesosternal segments are hour-glass shaped, with the inferior sur- 
face flat. The xiphisternal segment is longer than any of those preced- 
ing. Its inferior surface is also flat. Posteriorly, the transverse diameter 
increases slightly. 
Appendicular Skeleton. — Several more or less complete scapulae of 
P. australe are in the collections, of which the best preserved is figured 
on Plate IV, figure 10. The coracoid border above the suprascapular 
notch is moderately convex throughout, the convexity continuing un- 
broken over the vertebral border as far as the inferior angle. The axillary 
