CRETACEOUS PTERODACTYLES. 441 



or part answering to that marked 2 in Pterodacti/lus suevicus, and above by the sur- 

 angular (e). This element appears to have coalesced with the articular one; but 

 between the bone (", c) and that marked b a true harmonia or toothless suture 

 remains. The line below the letter e, in fig. 6, appears to be an accidental crack. 

 The fractured anterior end of the fragment (fig. 10) indicates the extreme thinness 

 of the wall of the bone, which consists of compact osseous substance. A part of 

 the concave, articular, surface is shown at a, fig. 7. 



A similar longitudinal depression on the inner side of the back part of the 

 ramus, with its lower boundary produced as a ridge, and formed by the angular 

 element (2), is indicated in the figure of the lower jaw of the Pferodacfi/lus suevicus 

 in Professor Quenstedt's memoir ; according to the proportions of which jaw, the 

 present comparatively enormous fragment would answer to almost the hinder half 

 of that part of the ramus which has not united with its fellow to form the long 

 symphysis, and it may be estimated as including one fourth of the entire length of 

 the lower jaw, which would give to the Pterodactyle, yielding the present mandi- 

 bular fragment, a head exceeding sixteen inches in length. It is probable, however, 

 that the head of Pterodacti/Ius simus was relatively shorter and thicker than in the 

 smaller species of Pterodactyle. 



The BaHi-occvpital (PI. 11, figs. 11, 12, 13). 



A skull of the size above indicated would require an occipital condyle at least 

 as large as that on the basi-occipital element figured in the above-cited plate. 

 This condyle projects backward on a well-marked base too broad to be called a 

 peduncle ; the convexity is only hemispheric, with the transverse diameter pre- 

 dominating; its shape and position indicate great freedom of movement of the 

 head upon the spine. There is no mark of a sutural surface for the exoccipitals on 

 the expanded part of the bone (5) ; they were probably confluent, as in birds, with 

 the basi-occipital, and have been broken away; the fractured surface (fig. 12, 6) 

 shows the large cancelli of this part of the occipital bone. The upper surface (a) 

 indicates a wider foramen magnum, or neural canal, than that of the combined 

 atlas and axis (fig. 14, k), and such a structure accords with the free and extensive 

 movements of the head upon the spine indicated by the form and prominence of 

 the condyle and its occipital cup (c). 



Atlas and Axis (PI. 11, figs. 14, 15, and 16). 



The anchylosed atlas and axis (figs. 14, 15, and 16) correspond in size with the 

 above-described basi-occipital ; they were obtained at the same time from the 



