1901.] BEPTlIiES FROM PATAGONIA. 177 



which is exposed between the opisthotic, parietal, and the bone at 

 the upper end of the quadrate. The fragment is doubtless the 

 highest point of the anterior otic bone, of which the upper part 

 is otherwise completely buried by the surrounding elements. The 

 parietals ([Xt.) occupy "nearly half the entire length of the cranium, 

 curve downwards to form the side walls, are much compressed in 

 their anterior two-thirds, and rise into a conspicuous sagittal crest. 

 They are flattened in the middle line at their anterior end, and 

 are not pierced by a pineal foramen. Each of the frontals (/V.) is 

 nearly three times as long as broad, and slightly widest at its 

 truncated anterior end. There is no supraorbital bone ; but pos- 

 teriorly and anteriorly the outer border of the frontal is shghtly 

 notched for the accommodation of the postfrontal and prefrontal 

 respectively. The postfrontal ( j)^/.) seems to have partly bounded 

 the comparatively small orbit (orh.) behind ; but this bar is broken 

 away on both sides. The prefrontal {pr.f.\ best preserved on the 

 left (fig. 1 «), is flattened and triangular in shape, almost equi- 

 lateral ; it is only slightly in contact with the postero-lateral angle 

 of the nasal bone. The nasals (««.) are also flattened and tri- 

 angular in shape, but antero-posteriorly elongated and with a 

 somewhat concave outer side which bounds the relatively large 

 narial opening {nar.). They are widest at their articulation with 

 the frontals. They are incomplete in front, and the premaxillse 

 are unfortunately not shown. The greater part of the palate is 

 obscured by matrix or broken away, but some features at the 

 postero-lateral angles of the cranium and in the facial region are 

 well shown. As observed especially on the left side (fig. 1), a 

 long and narrow plate of bone {s.t.) forms the postero-superior 

 boundary of the parietal and otic region, and seems to constitute 

 the articulation for the quadrate. This is doubtless the element 

 commonly named supratemporal in Snakes, Lizards, and Mosasaurs. 

 The quadrate {qu.) is evidently short and broad, but is only 

 imperfectly shown in section on the left side. Its remains (PI. XX. 

 fig. 1 c) are not readily interpi-eted ; but the upper end of the bone 

 seems to be displaced outwards and incomplete in the fossil, while 

 the more expanded lower end shows the large notch which usually 

 forms a loose articulation for the pterygoid in Snakes. At first 

 sight, it might be supposed that the quadrate was of the same 

 form as that of the Mosasaurs, with a deep posterior notch for 

 the auditory meatus ; but closer study seems to make this 

 interpretation impossible. At the side of the cranium, below the 

 supratemporal and parietal, the upper border of a large prootic 

 {-pr.o.) is exposed ; Avhile between this bone and the orbit the 

 downwardly cttrved portion of the parietal forms a sharp longi- 

 tudinal lateral ridge (v.). There are no traces of temporal arcades. 

 The short pterygoids {pt.) are partly exposed, and a portion of 

 the palatine below the orbit on the left side bears traces of two 

 comparatively minute teeth. There are distinct remains of an 

 ectopterygoid or transverse bone {ec.) on each side between the 

 pterygoid and maxilla ; and a fragment on the left side seems to 



