58 Field Columbian Museum — Geolooy, Vol. II. 



is slender. The two bones meet in a median suture on the under 

 side of the sphenoid, their posterior border forming a wide and deep 

 concavity. The outer margin of the bones converge from the quad- 

 rates as far forward as the posterior end of the interpterygoid vacui- 

 ties, where they curve outward into the posterior border of the ecto- 

 pterygoid processes. The under surface is shallowly concave on 

 either side back of the vacuities, but in the middle there is a rather 

 strong, obtuse ridge. A little back of the vacuities, on either side, 

 with their origins separated, a narrow and strong ridge arises to 

 curve outward and become lost on the under border of the somewhat 

 descending ectopterygoid process. In front of the vacuities the two 

 bones again meet in a long median suture. The palatal surface here 

 occupies a somewhat higher plane than that of the posterior part, and 

 is flat throughout. The bones of the two sides gradually narrow in 

 width to terminate by an obtuse extremity near the middle of the 

 palate. Between the ectopterygoid processes and between the curved 

 ridges already described there is a narrow, deep vacuity, with two 

 oval, elongated, well-defined foramina or vacuities at the bottom, the 

 " palatonares" of Owen, the "posterior palatine vacuities" of 

 Andrews, the "interpterygoid vacuities" of authors. A discus- 

 sion of their character will find a place further on. The lateral walls 

 of this fossa posteriorly are nearly vertical, but the anterior end of 

 the fossa is but little or not at all excavated above the plane of the 

 palate here. From the anterior end of the median posterior inter- 

 pterygoid suture two sutures diverge, leaving a large angular sloping 

 surface exposed which forms the posterior roof of the fossa ; the bone 

 exposed between the V-shaped sutures is the basisphenoid, and has 

 attached to it by suture the so-called parasphenoid bone in front. 

 Just how the diverging sutures terminate I cannot definitely say. 

 They seem to follow the lower angle of the lateral wall of the fossa 

 as far forward as the middle of the vacuities and thence return to join 

 the parasphenoid suture at the posterior part of the vacuities. If 

 this determination is correct, these projections would correspond to 

 the basipterygoid processes of the lizards. The ectopterygoid pro- 

 cesses of the pterygoids, the continuation of the curved ridges, have a 

 rounded, prominent under border, with a terminal, large, vertical or 

 oblique, abutting, mandibular surface. This ridge and its abutting 

 surface are very much as they are in Pliosaurus, and the whole struc- 

 ture here also reminds one of the crocodiles. 



The transverse, transpalatine or ectopterygoid bone is a rather 

 small, flattened polygonal bone, whose under surface is continuous 

 with that of the palatine and pterygoid in front. It joins the ptery- 



