0, C. Marsh — Characters of the order Hallopoda. 417 



The main characters of the posterior limbs are shown in the 

 figure below, which represents the bones of the left leg* and 

 foot, natural size, in the position in which they lay when un- 

 covered. All the bones figured are still firmly embedded in 

 the matrix. 



Left leg and foot of Hallopus victor, Marsh ; natural size ; side view, 

 a, astragalus: c. calcaneum ; d, tarsal; /, femur; t, tibia; II, second metatarsal; 

 V, remnant of fifth metatarsal. 



There are but two vertebrae in the sacrum. The other 

 vertebrae preserved have their articular faces bi-concave. The 

 chevrons are slender and very elongate. 



Taken together, the known characters of Hallopits indicate 

 Dinosaurian affinities rather than those of any other group of 

 reptiles, and if the Dinosauria are considered a sub-class, the 

 Hallopoda at present may be regarded as an order of Dinosaurs 

 standing more apart from typical forms than any other. 



The characters which now indicate the position of the 

 Hallopoda among the Reptilia, living and extinct, are given 

 below. The discovery of more perfect specimens, however, 

 especially of the skull, must be awaited before their nearer 

 affinities can be determined. 



DINOSAUMA ? 



Order Hallopoda (Leaping Foot). Carnivorous. 



Feet digitigrade, unguiculate. Fore limbs very small, with 

 four digits in manus. Hind limbs very long, with three digits 

 in pes, and metatarsals greatly elongated. Calcaneum much 

 produced backward. Vertebrae and limb bones hollow. Two 

 vertebrae in sacrum. Acetabulum formed by ilium, pubis, and 

 ischium. Pubes rod-like, projecting downward, but not 

 coossified distally. No post-pubis. Ischia with distal ends 

 expanded, meeting below on median line. 



New Haven, Conn., April 21st, 1890. 



