138 BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



range of this dinosaurian family. It also raises a serious question as to the correct- 

 ness of the accepted conclusions that the Arundel fauna is to be correlated with that 

 of the Morrison; but that question is beyond the scope of the present study and 

 will be treated elsewhere. 



In describing these bones Lull has contrasted them with the hind feet of Dryo- 

 saurus altus Marsh and Laosaurus consors Marsh, especially the former, and the 

 differences pointed out are invariably those which exist between Ornithopod and 

 Theropod hind feet, as clearly shown by a comparison with a foot of Camptosaurus 

 dispar Marsh (No. 5473, U.S.N.M.) and with a foot of Antrodemus valens Leidy 

 (No. 8423, U.S.N.M.), which are now before me. 



The left astragalus when viewed from below is somewhat hourglass shaped, 

 narrowing toward the calcaneal facet. That it pertains to a member of the 



Theropoda is clearly shown by the presence of 

 d fy an ascending process and its narrowness fore and 



aft as compared with its width. The ascending 

 process as preserved does not show its full extent, 

 IWHfik having been much worn down by abrasion. Lull 



l^-Wfi^ Im '•' \illH gives the following dimensions of this bone: 



lit. Hill Transversediameter m ; 8 



Greatest fore and aft diameter 50 



Least fore and aft diameter 26 



Height 56 



Metatarsal II, No. 5704, U.S.N.M., pertains to 



Fig. 71.— Metatarsals of Ornithomimus ,t • n , n , n • , i j. ,-, »■ , n , • 



affinis new species, cotypes. (a) distal the n S ht foot > and consists only of the distal artic- 

 end of right metatarsal in, No. 5684, ular end, as shown in figure 72b. I have compared 



U.S.N.M.. viewed from front. (6) Dis- •■ / n n j_i ±1 1. « n .. 7 . 



TAL END OF RIGHT METATARSAL II, No. 5704, lt («? Wel1 aS &U th& 0t ^ QT COtypeS of OmithomimUS 



tj.s.n.m. viewed from front, both affinis) with the same bone in the Ornithomimus 



FIGURES 4 NAT. SIZE (AFTER LULL). ^^ ^ ^ ^^ ^ ± ^ R _ JJ^^ and; except 



for being slightly heavier, is identical in all other respects. "The greater roundness 

 of the articular face, lesser prominence of the other outer keel," and the more pro- 

 nounced depressions upon the lateral faces of this metatarsal, as pointed out by 

 Lull in comparing it with D. altus, are all Theropod characteristics as mentioned 

 above. Its principal dimensions are as follows: 



mm 



Width of articular extremity 33 



Diameter, antero-posteriorly 34 



Greatest length of bone as preserved 54 



Width of shaft above articular end 29 



Metatarsal III, No. 5684, U.S.N.M., also pertaining to the right foot, consists 

 of the complete distal articular end and a considerable portion of the lower third 

 of the shaft as shown in figure 72. Since Lull figured this bone ' the working up 

 of the fragments has more than doubled its original length. 



It is identical in shape but slightly smaller in size than metatarsal III of the 

 Ornithomimus foot, with the exception that the transverse depression on the ante- 



1 Maryland Geol. Surv., Lower Cretaceous, 1911, pi. 19, figure 7, right, here shown as figure 73 A. 



