OSTEOLOGY OF CAEJ^'IVOROUS DINOSAURS. 71 



Measurements of the tibia of Antrodemus valens Leidy. No. 4734, U.S.N.M. 



Trim, 



Greatest length 690 



Greatest diameter of proximal end 210 



Greatest diameter of distal end 185 



Fihula (/.).— The left fil>ula of No. 4734, U.S.N.M., has suffered injury in life 

 on the distal fourth, and exostosial growth of the bone has greatly enlarged and 

 distorted this portion of the shaft, as shown in figure 48. The normal fibula is a 

 long, slender bone with a much expanded, antei'o-posteriorly proximal end and a 

 little enlarged distal extremity. Its length is slightly less than that of the tibia. 

 The proximal end is 



subcrescentic in outline, -^ ^ 



with the concave side ^.^<r A\\N\\w\\\\\ f«.. ^ 



toward the tiMa. The ^X^S^^^fc^lV Oi 



distal end is concave 

 from front to back with /^^wv ^ 



an upward turned lip ^^^^^^' ]^^^^^^l \ ^^^^^fT 



on the anterior face. /^^^^^^^^^^3 • r\ ~ '^ 



This end articulates ex- T^i'^^^^^^^^^^ W' 



clusively with the cal- 



caneum, though the ^^^^^^^^i^^^ /f 



internal side is in con- 

 tact with the ascending 

 process of the astrag- 



1 i,* 1, '4. T 1 i-1 Fig. 49. — Proximal and distal ends of articxtxated left tibia, FiBirLA. astragalus, 



alUS, WniCn it Sllglltly and CALCANEUM of antrodemus VALEN.'i LEIDT. No. 4734, U.S.N.M. J NAT. SIZE, 



overlaps. The inner '^' '■RO'^im-*!- '^ni' -B, distal ends, as, astragalus; ca, CALCANEUM; /,- fibula; 



face of the fibula on the 



lower two-tliirds is flattened, the flattened area becoming wider as the distal end 

 is approached. This flattened side is closely applied to the tibia, especiall}- the 

 Ipwer third, as shown in figure 48. 



Measurements of fibula of Antrodemus vahns Leidy. No. 47S4, U.S.N.M. 



mm. 



Greatest length of fibula 623 



Greatest diameter proximal end 145 



Diameter distal end (antero-posterior) 59 



Diameter distal end (transverse) 49 



Least diameter shaft 32 



Tarsus. — The tarsus in Antrodemus is composed of four bony elements, the 

 proximal row formed by the astragalus and calcaneum, the distal row by two dis- 

 coidal bones, probably tarsalia three and four (fig. 49) . 



Calcaneum (Ca.). — The left calcaneum of No. 4734, U.S.N.M., in position is 

 closely applied to the outer side of the astragalus and in advance of the tibia. It is 

 narrow transversely, with the antero-posterior diameter exceeding the vertical. 

 The upper articular surface is markedly concave from front to back, being deepest 

 toward the front. It is rounded below and in front in an irregular semicircular 

 curve. 



The outer free surface is concave, with a raised anterior border. The inner 

 surface appears to be concave in its contact with the tibia; the portion in contact 

 with the outer face of the astragalus appears to present an angular conve.x face. 



