224 PROE. H. Gt. SEELET ON ARISTOSTJCHUS PT7SILLTJS. 



which extends like the metal of an adze from the haft. Where the 

 bones are fractured proximally they are compressed from side to 

 side, and extend upward with a slight sigmoid curve inward, which 

 is completed distally by the convergence of the bones. At the 

 proximal fracture the bone measures 12 millimetres in the antero- 

 posterior direction, and 6 millimetres from within outward, with 

 the borders rounded in front and behind, but a linear muscular 

 furrow ascends the inner posterior border of the bone. As the bone 

 expands a little in antero-posterior extent as it extends proximally 

 it curves a little forward, making the anterior border of the proximal 

 end of the bone slightly concave, and the posterior border very 

 slightly convex. All the middle portion of the bone preserves about 

 the same antero-posterior measurement of 8 millimetres ; but dis- 

 tally the measurement increases by an expansion which is chiefly 

 behind the median axis of the bone, till at its line of junction with 

 the posterior distal expansion its width is 2*5 centimetres. 



The middle of the shaft is well-rounded externally, but as the 

 bone widens distally this external surface begins to be flattened till 

 it merges in the flat distal posterior expansion. But the middle of 

 the shaft is compressed from front to back, so as to form a sharp 

 internal edge, and here the measurement from within outward is 

 13 millimetres. This sharp internal ridge is 6 centimetres long and 

 paiallel to the external outline. In this region of the bone the 

 anterior face is convex from within outward, while in length there 

 is a very slight convexity. The posterior aspect is flattened. 



Distally for a length of fully 3 centimetres the bone is compressed 

 from within outward. Anteriorly something of the distal teimina- 

 ticn may be lost, but the mass preserved extends posteriorly for 9*3 

 centimetres, with a perfectly straight flat base, which is 1*5 centi- 

 metres wide in front, and narrows posteriorly to a few millimetres. 

 A median groove deepening in front extends along the anterior end 

 of the base for 3*5 centimetres. The lateral surfaces of this posterior 

 keel are slightly concave ; they converge upward to a sharp keel, 

 which has a gently convex contour, as it tapers posteriorly to a 

 blunt point ; its depth near the shaft is 2 centimetres. 



Both the pubic bones are slightly displaced distally, where they 

 unite with this keel, and these junctions, which are not quite sym- 

 metrical, have been regarded by Sir K. Owen as sutures. The 

 point is difficult. The anterior extremity of the bone was certainly 

 cartilaginous, and the anterior extremities of the pubes are exposed, 

 distinct from each other, and distinct from the keel ; but this is 

 hardly conclusive evidence of separate ossification, which is not 

 improbable. Proximally a small fragment of a thinner bone is 

 seen, posterior in position, which may have belonged to the ischium. 



The only animals with w T hich this form of pubis can be compared 

 have been described by Prof. Marsh as Ccelurus, with which genus 

 Prof. Marsh identifies the specimen now described *. So far as I 

 can judge from the figures given by Marsh, it is simply proved to 

 be closely related to Allosaurus, Coelurus, and Ceratosaurus, and 



* American Journal of Science, vol. xxvii. p. 335 (April 1884). 



