22 ■ Fikld Columbian Museum — Geology, Vol. II. 



pterygoid articular surface reaches to within about twenty-five milli- 

 meters of the articular extremity. The inner border of the pit is 

 produced forward for articulation, apparently, with the paroccipital. 

 The two narrow, concave, articular surfaces for the squamosal and 

 quadratojugal are separated by a narrow, non-articular ridge. They 

 both extend very nearly to the cotylar surface of the bone. 



The pterygoids articulate posteriorly by a deep, pit-like suture 

 with the inner side of the distal extremity of the quadrate; the latter 

 does not send out a process to meet the bone. The bar connecting 

 the quadrate with the body of the bone is oval in cross-section, with 

 a rounded inferior border. It is about thirty millimeters in length 

 and is placed obliquely; it does not extend much posteriorly to the 

 coronal plane of the occipital condyle. In front of this quadrate 

 process there is an elongate, flattened or concave plate, with nearly 

 parallel sides, separated from the parasphenoid by a slender, elon- 

 gated vacuity. * At the posterior extremity of this plate there is a nar- 

 row bridge connection with the basisphenoid. The connecting suture 

 is not determinable, so that one cannot say whether the two ptery- 

 goids meet here in the middle, as in Pcloneustcs and P/iosa/irits, or are 

 separated, as in Plcsiosaurus. In front of the interpterygoid vacuity 

 the pterygoids unite with the parasphenoid broadly; here also the 

 connecting suture cannot be determined. Opposite this connection 

 exteriorly, the bone sends out a stout process for union with the ecto- 

 pterygoid or transverse bone. Back of both of these, and on the inner 

 side, near the margin of the vacuities above, there is the attachment 

 of a stout epipterygoid pillar, passing upward, and apparently a little 

 inward to unite with the lower anterior part of the parietals, as 

 already described: both extremities are tumid, and the connecting 

 sutures cannot be determined. The rod is broken on both sides in 

 the specimen near the parietal end, and, as preserved, is curved for- 

 ward. It is oval in cross-section, with the greater diameter of about 

 ten millimeters; the entire length is thirty millimeters. Anteriorly, 

 the pterygoid sends a flattened process to meet the posterior extremity 

 of the vomers; it is flattened and pointed. This process is gently 

 expanded at each extremity, especially the proximal; it has a smooth, 

 thin edge on each side, except at the distal end, where it meets its 

 mate, suturally, in the middle. Between the two processes there is 

 an elongate, oval vacuity, which is not filled by the ossified para- 



* Andrews calls this opening the posterior palatine vacuity or foramen; hut this term is more 

 properly restricted to the opening between the palatine, pterygoids and maxilla;, corresponding to 

 the posterior palatine foramina of mammals, and is thus used in the Chelonia— the sub- or infra- 

 orbital vacuity of Andrews and other authors. 



