90 O. C. Marsh—American Jurassic Dinosaurs. 
is briefly discussed, and both will be more fully described ina 
future communication. 
The genus Allosaurus is typical of the family, which also 
includes Creosaurus, and Labrosaurus. The first named genus 
presents some very interesting features in the vertebra, and 
pelvic arch. The vertebrae first described are remarkable 
nearly vertical, or somewhat divergent above. The exa 
form of the ilium is not known with certainty, and in the d 
position solve many difficulties in the structure of the Din 
rian pelvis, especially in the Carnivorous types. At its pro 
mal end, this bone has four well-marked articular faces; one 
in front for the ilium; next the acetabular face; an obliq 
figure (Plate VIII, figure 2, p’). The shaft of the pubis 
slender, and the distal end is expanded longitudinally, and 
firmly codssified with its fellow. he two seen from the ir 
ei 
remarkably narrow one. 
