Emerson and Loomis — Stegomus Longipes. 379 



cave and with long transverse processes. Two vertebrae only 

 are involved in the sacrum, their moderately long transverse 

 processes supporting the ilium. How completely they are 

 united is not clear on account of the broken condition of the 

 vertebrae, but they appear slightly separated. Three and a 

 half deeply biconcave caudals are all that are preserved. The 

 transverse processes of these are even longer than on the pre- 

 sacrals and quadrate in section. From the sacrum back they 

 are progressively longer, suggesting a broad flat tail such as is 

 known for Aetosaurus. 



Fore Limb. — Of the pectoral girdle only the scapula is pres- 

 ent, and this is a broad triangular bone 9 Inm long by 5 mm deep. 

 Its upper margin lies parallel to small lateral plates 7-9 in the 

 series. The leg is unusually long, the slender humerus being 

 1-J inm in diameter and 24 mm in length, a bone nearly straight 

 and swelling slightly at either end. The radius and ulna are 

 but f mm in diameter and 19 mm long. As the specimen lies, the 

 radius crosses the ulna, but whether this indicates great flexi- 

 bility or is mere chance is not to be determined. The fore 

 foot is lacking. 



Hind Limb. — An ilium 12 mm long, the front and rear ends 

 of which curve strongly outward, is present, bul only its rough 

 outline is to be made out. Of the limb bones only short frag- 

 ments are discernible, where they are broken across; but 

 enough is visible to show the direction and diameter of the 

 bones, and by extending these the length can be approximately 

 found. This indicates a leg slightly longer than the fore leg. 

 The femur was l-| mm in diameter and 26 mm in length (by 

 reconstruction). The tibia and fibula are each about the same 

 size, f mm in diameter and 21 mm long (by reconstruction). The 

 left foot is well preserved. The individual tarsals are not to 

 be made out. Four toes are well preserved, but a fifth is 

 nowhere even indicated. The length of the toes on the figure 

 is probably a little short, as each seems incomplete at the end. 

 The metapodials are long, but the details of the toes do not 

 come out with certainty, though a slight widening at intervals 

 was taken to indicate the joints, and they are drawn on that 

 supposition. 



Comparison. — This animal resembles most closely Marsh's 

 Stegomus a?*cuatus, of which twenty dorsal sets of plates are 

 described. It is a much smaller species and presents most of 

 the important features, thus allowing a conception of the ani- 

 mal and its relationships. Stegomus longipes is about one- 

 third the size of the preceding species, which is the only com- 

 parison readily made, as Marsh's fossil is so incomplete. It 

 belongs to the Aetosauridae* and resembles that genus in many 

 important features, but there are enough characters of weight 

 to demand a separate genus, as established by Marsh. Ornitho- 

 * Fraas O. 1877, Wiirttemb. naturw. Jahreshefte, xxxiii, Festschrift. 



