The smallest specimen is a compressed sub-semicircular bone 1-1/4 inch long, 9/16 inch high, and a 1/4 inch thick. The under surfaces converge to form a strong keel, which is flattened off behind. Above this, the posterior third of the bone is compressed obliquely to half the thickness, as though a bone had over-lapped this area on each side. If the oval spaces are nares, that bone might have been the pterygoid or palatine. Three-fifths of the remainder of the bone are taken up by the smooth oval depressions, which might be the inner walls of the nares; and above this is a margin of bone widening into the triangular compressed part in front, which, if the fossil is rightly determined, must have fitted into the posterior end of the maxillary or anterior end of the palatine bones. A specimen collected by the Rev. T. G. Bonney is preserved on the sacral side of a left _os innominatum_ with the keel downward. It appears to show a sutural surface from which an anterior part has come away. And if this specimen is compared with the neural arch of the sacral vertebra =J=._c_.4.1, it will be found to correspond entirely. It is not impossible that _c_.10.1, 2 may be vomerine, and _c_.10.3 sacral, but there are no distinctive characters between the specimens to warrant such a determination. QUADRATUM. Pl. II. and Quadrato-Jugal. Case. Comp. Tablet. Specimen. =J= _c_ 11 1-4 In the Woodwardian Museum are two distal ends of the quadrate bone and two other fragments showing the quadrato-jugal with it. _Quadrate._ The smallest specimen is 1/2 an inch over the articular surface for the lower jaw and a quarter of an inch thick. It is concave from side to side in front where it shows a large pneumatic foramen near the basal end; it is bent from the articulation a little backward. It is convex behind; and between the foramen and the articulation sends inward and forward a great wing like that of the quadratum in birds. The specimens are broken short off and do not show any articulation above, where the bone contracts. The distal articulation is double, like two long cones placed together; that in front having the base outward, while the hinder one has the base on the inner side. The largest specimen, which is much broken, shows the articulation half an inch thick. _Quadrato-jugal._ This is a thin flat squamous bone, apparently of a transverse diamond shape, which is anchylosed to the anterior lateral margin of the quadrate, at right angles to the articulation. The lower margin is straight, as is the upper anterior margin, which appears to have received the malar bone above. The upper posterior side is broken, but shows a large foramen near to the side of the quadrate. The base of the diamond is at the articulation, and at its apex is a small fragment of smooth surface, either part of a foramen, or the orbit of the eye.