AND AYES OF NORTH AMERICA. 91 separated by a concave margin from a larger portion at right angles to the shaft. The latter bears an oblique surface for fixed articulation at its extremity. In Megaclactylus,* the distal portions of the ischia are united on the median line for a considerable distance, and are styloid in form. This portion is evidently distal, from the lack of articular faces and the divergence and flattening of the other extremities. They also resemble the distal extremities in Compsognathus. In Clepsysaurus, the shaft and di-lated extremity are both preserved. The former resembles that of Megadactylus, the latter that of Hadrosaurus in some degree. If the shaft be posterior, the other extremity is an-terior, and the larger dilatation extending at an angle to the shaft supports, no doubt, the iliac articulation. The trihedral shaft indicates a median line of junction. In Hadrosau-rus no part of the shaft presents a face for contact with that of the other side, while in lielaps such face is very distinct and elongate. From the above, I suppose that the larger extension of the ischium is superior and bears the iliac articulation, that the concave an-terior outline is that bounding the acetabulum, and that the lower dilatation was in con-tact with but not united to the pubis. This. is the more probable, since it agrees nearly with the arrangement in Iguanodon, as pointed out by Hutley.t It cannot be denied, how-ever, that the supposed iliac articulation in the ischium in Hadiosaurus, bears a remark-able similarity to the median suture presented by the union of the two supposed ischia on the middle line below and distally, as in the pubes of Struthio. In that case, they would be pubes. In a posterior direction and median approximation it will agree also with the known pelvic elements of an interesting Saurian described by Von Meyer (Palaeonto-graphica) from the '\Vcalden of Germany, the Stenopelix valdensis. No attempt has been made, so far as I am aware, to refer this animal to its place. It appears to me in its ver-tebral and pelvic features to be a small Dinosaur allied to Scelidosaurus Owen. The ischia, however, are remarkably prolonged posteriorly, and find a parallel in Compsog-nathus Wagn. Believing them to be ischia, the inferior pelvic arches of Hadrosaurus were light and slender, the ischia parallel and light, and entirely incapable of supporting the weight of the animal, as was done by Megadaetylus. The tail was no doubt the great support when the head was elevated.
- The large pneumatic foramina, in the vertebrre of this genus, together with those seen in the sacrum of Lrelaps, explain the character of similar vertebite described as os quadratum of Iguanodon by 3Iantell and Owen, and saerals of Hadrosaurns by Leidy. I regard the latter as indicative of a new genus allied to the Goniopoda.
.1. Opportunity of reviewing this part of my essay baying offered, I must point out the confirmatory evidence I have derived from Prof. Huxley's recent explanation of the structure of Hypsilophodon, with regard to my determin-ation of the pnbes in Hadrosaurus. He proves conclusively its posterior direction, which view I adopt for Hadrosau-ms, contrary to my former supposition. AMERI. PITILOSO. SOC.-VOL. XIV. 25
