532 Mr. R. W. Hooley on the 



inciiided the greater portion of tlie hinder part of the sknll 

 of Oniithostoma {Pteranodun), from the posterior moiety of 

 the orbits to the occiput, showing the base of a true and 

 })0\verful supraoccipital crest. This interesting fossil he 

 described and figured^ as the orbito-ethnioid-sphenoid bone. 

 The tablet J. c. 9, upon which this specimen is mounted, 

 has been labelled " Ethmoid with basisphenoid."^ An ink- 

 line has since been drawn through this, and someone has 

 written "Parietal with supra-occipital.^' A cast in wax of 

 the aspect shown in Seeley's fig. 9 is also on the tablet 

 marked '' cerebral hemispheres and pineal body." lx\ 

 pi. xi. fig. 8 * the left side is shown. As the bone is figured, 

 the occiput is horizontal, whereas it should be oblique, 

 llie hinder border of the orbit is seen on the left upper half 

 of the bone. The base of the supraoccipital crest extends 

 from the top right-hand corner of the figure to the emar- 

 ginatiou near the lower. Fig. 7 * is a portion of the occiput 

 placed upside down. The indentation in the upper border 

 of the figure is the dorsal half of the foramen magnum, 

 while the two foramina on either side below are the post- 

 temporal fossae {cf. PI. XXII. fig. 2) . The hinder moieties of 

 the orbits are preserved, and are exhibited in fig. 9, pi. xi. 

 In Seeley's explanation of the figure they are called "the cups 

 which covered the anterior termination of the cerebral lobes," 

 The cerebral hemispheres are not exposed at all. The 

 frontal bone immediately posterior to the orbits is greatly 

 compressed, becoming a deep strong keel, which intensifies in 

 the parietal region. Here, where it meets the upper border 

 of the occipital plane, it shows the base of a crest which is 

 destroyed, but, from the section of the bone, it was deep and 

 robust and produced far beyond tlie occiput, as in Ornitho- 

 stoma (Pteranodon) (PI. XXII. fig. 1). It has no connection 

 with the occiput, which lies below it. The occipital area 

 preserved is small and triangular. There is a strong median 

 vi'rtical ridge to the foramen magnum, on either side of 

 which the surface is concave. In the centre of these 

 surfaces, slightly above the level of the foramen, are the 

 post-temporal fossie, which are small and subcircular. The 

 skull below the dorsal half of the foramen magnum is 

 destroyed. 



The back of the skull J. c. 8, 2 is the type of Ornitho- 

 cheirus, and J. c. 9 belongs to Oi'uithosioma [Pteranodon) , 

 and the two genera are totally distinct, as the muzzles also 

 jirove. The genus OrnUhuclteirus has been given all the 



* II. Q. Set'loy, ' Ornitliotiauria,' IfiH), pp. 85, 80, pi. xi. figs. 7-9. 



