62 



THE CERATOPSIA. 



THE HIND LIMB AISTD FOOT. 



The hind limb and foot in Triceratops is longer than the fore limb and somewhat more 

 slender, though it also may be regarded as robust. 



THE FEMUR. 



The femur is half as large again as the tibia. The shaft is constricted and somewhat 

 elliptical in cross section, with the transverse diameter the longer. It is much expanded at 

 either extremity. Proximally the head is well differentiated from the shaft and the greater 

 trochanter by a marked constriction or neck. It is directed upward and inward at an angle of 

 about 45° to the longitudinal axis of t"he femur. The articular surface of the head is rugose 

 and exhibits a convoluted structure, which is continued out upon the superior surface of the 

 greater trochanter. The latter is expanded antero-posteriorly, inclosing externally a deep 

 digital fossa. About midway between the head and the distal end of the femur there is a 

 rudimentary fourth trochanter situated on the postero-internal border of the bone. The distal 



end of the femur is rather more expanded 

 transversely than antero-posteriorly. The 

 external condyle is larger than the internal. 

 The intercondylar notch is very deep and 

 narrow. The external condyle sends back- 

 ward a considerable projection, which is 

 narrow and constricted just opposite the bot- 

 tom of the intercondylar notch. The prin- 

 cipal characters of the femur are well shown 

 in fig. 71 and Pis. XIV and XV. 



THE TIBIA. 



The tibia is short, much constricted medi- 

 ally, but greatly expanded at either extrem- 

 ity. At the distal extremity this expansion 

 is almost entirely in a transverse direction, 

 there being no marked antero-posterior ex- 

 pansion. There is no well-defined internal 

 malleolus on the inner side, but the external 

 border is developed into a very prominent 

 process, forming somewhat less than one-half 

 the distal extremity of the tibia. This process 

 falls a little below the inferior border of the astragalus and closely embraces that element 

 on its external surface. It may be regarded as having performed the same functions as did 

 the external malleolus or distal end of the fibula in the Mammalia. Its anterior surface was 

 in contact with the distal extremity of the fibula. The principal characters of the tibia are 

 shown in fig. 71 and PI. XVI. 



THE FIBULA." 



I have not observed this bone in the genus Triceratops or any of the Laramie forms of the 

 Ceratopsia. It was doubtless present, however, though much reduced. In describing the genus 

 Triceratops Marsh 6 says of it: "The fibula is very slender and the distal end was closely applied 



i An admirably preserved fibula was found with the skull (No. 970, American Museum of Natural History) described by Lull as pertain- 

 ing to Triceratops serratus Marsh. This bone, which is here figured (fig. 72), is long and very slender, withasubcylindrical shaft and flattened, 

 expanded extremities. Proximally the bone is crushed so as to exaggerate the flattening to some extent. The face which was applied to 

 the tibia is plane, while the outer surface is convex. The articular face is rounded and rugose. The distal articular extremity is much 

 flattened and was evidently closely applied to the front of the tibia. The articular face is concave and oblique with reference to the long 

 axis of the shaft. A somewhat roughened area of considerable size, for muscular attachment, occurs on the outer surface of the shaft about 

 one-third the length of the bone from the. distal end. — R. S. L. 



& Dinosaurs of North America, p. 214. 



D 



Fig. 70.— Phalanges of the manus of Triceratops serratus, No. 970, Ameri- 

 can Museum of Natural History. A, B, Intermediate phalanx, 

 viewed from the front and side; C, D, ungual phalanx, viewed from 

 front and side. One-half natural size. Drawn by R. S. Lull. 



