I903-] 



Hay, North American Cretaceous Fishes. 



1874, pi. vii.). There is, however, satisfactory evidence of 

 a pair of bones, or more probably of an unpaired bone with 

 right and left wings, which is placed in front of the alisphe- 

 noids. This bone, niarked o. s. in Figure 28, is certainly not 

 the lower surface of the frontal, and there is a plain suture for 

 union with the alisphenoid. The lateral edge of this bone is 

 not so certainly determined, but seems to be where drawn in 

 the figure. The surface for articulation with the large median 

 bone (Figs. 28, 30, p. sp.), lies about 10 mm. to the left (right 

 in the figure) of the midline between the frontals. This dis- 

 tortion could not occur if the bone {p. sp.) were articulated 

 to the under surface of the frontals. Hence, I hold that the 

 bones o. s. are the distinct, or more probably united, orbito- 

 sphenoids, while the bone {p. sp.) is the presphenoid. The 

 latter would occupy the position of the presphenoidal carti- 

 lage shown in Fig. 10 of PI. v and Fig. 10 of PL vii of Parker's 

 paper just quoted. Dr. Loomis's figure of A. alius also shows 

 an arch of bone running upward and outward from the upper 

 edge of the bone called by him orbitosphenoid. It is above 

 these bones that the anterior portion of the brain and the 

 olfactory nerve must have lain. 



The parasphenoid of this specimen must have had a median 

 process behind, like that represented in Loomis's drawing 

 (Fig. 10, PL xxii). At the anterior end of the 

 lower surface of the supposed prootics, in the 

 midline, there is an excavation in which this pro- 

 cess must have been lodged. As already stated, 

 the parasphenoidal grind- 

 ing plate is deeply pitted 

 (Fig. 29). Where a small 

 fracture occurs it is seen 

 ~ . that these pits pass down 



Fig. 29. A nog- J^ ^ 



mius alius? -^o tlic bone of the ordin- 



(Loomis). Same 



individual as g^j-y gort on which the ,,^'^-.30. 



Figs. 27, 28. X 2- •' (Loomis). 



Parasphenoid, dcnSCr maSS rCpOSCS. Ac- Figs. 27-29. X i Lateral view of 



Anogim'us altus ? 

 Same individual as 



palatal surface. 



parasphenoid and presphenoid. 



companying this plate is 

 another bone which is represented by Fig. 31. This was 

 broken, and the injured end has been ground down to show 



