ON THE SKULL OF NYCTODACTYLUS 52 1 



or laterally flattened bridge of stout bone, gradually and nearly 

 uniformly decreasing in width posteriorly to an acute point 

 between the frontals near the middle of the orbits. Its margins 

 are rounded as far back as the union with the anterior pro- 

 cesses of the frontals, which continue the same convex borders 

 to the free margin of the orbits. The sutures separating the 

 bone from the frontal posteriorly are indicated by lines exactly 

 alike on the two sides, and hence evidently sutural. On the 

 sides the union with the maxillae is indeterminate. If this union 

 is as in Rhamphorhynchus, as described by Woodward, 1 its posi- 

 tion would be back of the anterior end of the nares. In Scaph- 

 ognathus, however, Plieninger 2 would locate the suture at the 

 anterior extremity of the nares. Its alveolar borders form 

 straight, sharp, smooth ridges, with the inner wall two or three 

 millimeters in width, meeting the palatal surface at an angle of 

 about 135 degrees. The middle portion above is regularly 

 rounded, forming an arc of about a third of a circle. This por- 

 tion has its walls distinctly thicker than elsewhere, and has 

 resisted compression ; the sides from this median convexity 

 seem to have been gently convex, meeting the middle convexity 

 in a shallow groove. The surface is smooth, as in Ornithos- 

 toma (Pteranodoii), without pits or depressions. As in that genus 

 the texture of the bone of the beak has a distinct fibrillation 

 longitudinally, sufficiently well marked to enable one to distinguish 

 fragments from this part of the skeleton ; a fact long since 

 recognized by collectors of these animal remains in the field. I 

 am convinced there were no pits, depressions, or conspicuous 

 foramina on the premaxillary, and that neither in this genus nor 

 in Ornitlwstoma was there a longitudinal ridge in the middle 

 above. The proof of this is positive in both this genus and in 

 Ornitho stoma. On the under side, the bone forming the palatal 

 surface, in part probably composed of the premaxilla, in part of 

 the vomers, is of extreme tenuity, of the thickness of ordinary 

 writing paper. It appears to have been gently concave through- 



I Ann. Mag. Nat. Hist., Vol. IX, No. 2, 1902. 



2 Paleontographica, Vol. XLI, p. 203, 1894. 



