. The Quarterly journal of the Geological Society of London. vewhat must have been the orbit, there is a downward process, havingupon it a bone with a rugose surface, o b, which it is thought may,perhaps, be a supraorbital, but is most probably one of the hinder-most of the series of bones which surrounded the orbit. The formof the upper part of the frontal seems to indicate that this region ofthe skull was raised into a prominent crest; and this is a characterwhich Prof. Cope has shown to exist in other species of the genus. Whether the bone in the region of the letters pa is a portion ofthe
. The Quarterly journal of the Geological Society of London. vewhat must have been the orbit, there is a downward process, havingupon it a bone with a rugose surface, o b, which it is thought may,perhaps, be a supraorbital, but is most probably one of the hinder-most of the series of bones which surrounded the orbit. The formof the upper part of the frontal seems to indicate that this region ofthe skull was raised into a prominent crest; and this is a characterwhich Prof. Cope has shown to exist in other species of the genus. Whether the bone in the region of the letters pa is a portion ofthe parietal or not it is impossible to say; but certain it is thatimmediately below the letters this bone is suturally united with theone which has been called alisphenoid. The sclerotic is well ossified, and parts of four or five plates arepreserved; but neither of them is sufficiently perfect to show itsprecise form. 518 E. TULLEY NEWTON ON THE REMAINS OF Hypothetical restoration of the skull of Portheus gaultinus(see PI. XXII. figs. 1, 2, & 4). ;. bs. Upper portion of basisphenoid. as. Alisphenoid. pa. Parietal region, ps. Presphenoid. fr. Frontal, Sphenotic (postfrontal). Prootic. Opisthotic or exoccipital. ob. Supraorbital. pmx. Praemaxilla. mx. Maxilla, ju. Jugal. pi. Palatine. Prefrontal, eth. Ethmoid, olf. Perforation for olfactory nerve. HYPSODON ETC. FROM BRITISH CRETACEOUS STRATA. 519 The outline of the entire skull has been introduced in the annexedwoodcut, to render the relative positions of the parts more intelli-gible. The relation of the bones of the ethmoidal region to the maxillaand praemaxilla is quite certain; for, although now separated, thebroken surfaces show precisely how they fit together. The directionof the outline-base of the skull is determined chiefly by the directionof the under surface of the vomer. In placing the brain-case in theposition it occupies, regard has been paid to Prof. Copes figures ofPortheus, as well
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Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
