2 
This brief review shows there are at this time two adequately distinct 
genera of the smaller carnivorous dinosauria known from the Belly River 
formation of Alberta, Struthiomimus and Dromceosaurus . Whether 
Ornithomimus, the genotype of which comes from the much more recent 
Denver formation, is also represented in this fauna remains to be deter- 
mined. 
That the Geological Survey specimens about to be described are 
distinct from Struthiomimus and Ornithomimus can, it seems clear, be well 
demonstrated. Their distinctness from the contemporary Struthiomimus 
is at once shown by the great irregularity in length of the digits of the 
manus; the deeply grooved ginglymoid distal facets of me. I and II; the 
much longer and more slender proximal phalanx of digit II; the much 
shorter me. I; the less divergent pollex, and the more strongly curved 
raptorial type of unguals. Typically it is also a form of smaller size. 
From the Denver-Lance Ornithomimus this manus is distinguished by its 
larger size, and its Coelurid-like structure, as shown by the unequal lengths 
of the known metacarpals that have deeply grooved ginglymoid distal 
facets; as contrasted with the metacarpals of subequal length that have 
convex condylar facets, as in the genotype Ornithomimus velox Marsh. This 
distinction rests upon the metacarpus figured by Marsh 1 , a referred specimen 
and not a part of the type individual, but this association is probably 
correct, since the same features are to be observed in the manus of Stru- 
thiomimus, which has a pes that, except for its larger size, is almost indis- 
tinguishable from the hind foot of the type of Ornithomimus velox. 
The distinctness of the Geological Survey specimen No. 2367 from 
the contemporary Dromceosaurus albertensis cannot be established with the 
same degree of assurance because of the very incomplete nature of the 
known foot materials of Dromceosaurus, and the uncertainty as to whether 
these pertain to the manus or to the pes. Through the kindness of Dr. 
W. D. Matthew the foot materials of Dromceosaurus have been loaned me 
for study. After a careful comparison with the specimen here under 
consideration I share to some extent his doubt as to whether they pertain 
to the fore or the hind foot. From analogy it would appear that one of 
the metapodials of Dromceosaurus certainly belongs to the manus. Refer- 
ence is made to “the distal half of a metapodial slightly larger than the 
me. II of Struthiomimus 2 3 ” , which has a deeply grooved ginglymoid distal 
facet and a very distinct lateral appression surface. If this bone does not 
pertain to the manus, it represents a style of distal articulation the like 
of which has never before been known, so far as I can discover, in the 
metatarsals of a carnivorous dinosaur. Matthew has called attention 
(page 385) to the probability of three of the phalanges fitting so closely 
that they appear to belong with this metapodial, and from this concludes 
that “it must be the fourth digit, not the second, and may belong to the 
pes instead of the manus.” I see no reason why it may not be the third 
digit of the manus lacking only the ungual. The relative shortness of the 
phalangials certainly suggests hind-foot structure, but equally short 
elements are found in the fore foot of Ceratosaurus nasicornis 3 Marsh. 
1 “Dinosaurs of North America," U.S. Geol. Surv., 16th Ann. Rept., pt. 1, 1896, PI. 58, Fig. 4. 
2 Matthew and Brown, Bull. Am. Mus. Nat. Hist., vol. 46, art. VI, 1922, p. 384. 
3 Bull. 110, U.S. Nat. Mus., 1920, pp. 104, 105, test Figs. 60 and 62. 
