HOLLAND AND PETERSON: OSTEOLOGY OF THE CHALICOTHEROIDEA. 325 
Measurements (No. 1604). 
Mm 
Length of second right rib. Measured in a straight line...... Ftd Ad eee 444 
Diameter of upper portion including head.........................-+---- 68 
Greatest diameter of shaft near the middle, estimated.................... 45 
Greatest diameter of shaft near end, estimated..................---.+0--- 45 
The Third Rab. 
The third rib is nearly twice as long as the first rib; the neck supporting the 
head is reduced in length; the shaft is convex externally. Distally for two-thirds 
of its length it is flat or very slightly concave internally. Below the tuberculum 
on the internal side is a deep groove tapering at its distal extremity and terminating 
about one-third of the length of the rib near the posterior margin. 
MrAsuREMENTS (No. 1604). 
Mm 
Length of third right rib. Measured in a straight line.................... 546 
Dianreteromupper pornonyincludings header erin ene or eae are Nera 66 
Greatest diameternof shatt mean thepmiddles. 7 0... se 1-6 ey hens ee 40 
Greatest diameter of shaft near end, estimated.............-.-+0+--+-+ee 51 
The Fourth Rab. 
The neck supporting.the capitulum is slightly longer in this rib than in the 
third rib. The shaft externally is convex; internally it is flattened and about the 
middle slightly excavated. Below the tuberculum the transverse diameter of the 
rib increases and its antero-posterior diameter diminishes. On both the anterior 
and posterior surfaces below the capitulum there is a deep groove, which gradu- 
ally diminishes until it disappears about one-third of the distance from the head of 
the rib. 
Mrasurements (No. 1604). 
Mm 
Length of fourth right rib. Measured in a straight line................... 580 
Diameferonupperportionwmmecliaimngynead en aes ene eke hs else 1 71 
Greatestidiameter of shattmear the middle. 2.00 .....:-)4+-+:2---2+:05-- 40 
Greatest diameter of shaft near end, estimated................--..+--+++- 47 
The Fifth Rib. 
The fifth rib is somewhat longer than the fourth. The transverse diameter 
of that portion of the rib immediately below the tuberculum is greatly increased 
and a well defined angle is developed beyond the tuberculum. The anterior and 
posterior grooves beyond the tuberculum are as long as in the preceding rib, but 
somewhat shallower. The rib on its external surface is convex; on its internal 
