320 MR. W. K. PARKER ON THE OSTEOLOGY OF BALANICEPS REX. 
N.B. These are amongst the most constant cranial elements in all the Vertebrata, 
and are the most important of the ‘ periotics.’ 
3. The anterior infero-lateral elements—the ‘ ali-sphenoids.’ 
N.B. These elements are very constant in Mammals and Birds. They are large 
in the Crocodilia, but feeble and inconstant in the rest of the Abranchiate 
Reptilia. They are not ossified in the Batrachia, and are generally very small 
in osseous Fishes. 
4. The supero-lateral elements—the ‘ squamosals.’ 
N.B. These elements are large and well-developed in Mammalia, Birds, and 
Abranchiate Reptiles; they are scarcely differentiated in the Batrachia, and 
they are large and constant in the osseous Fishes. 
. Upper elements—the ‘ parietals.’ 
N.B. These are very constant throughout the Vertebrata, but are separated from each 
other in certain Carnivora, and in some osseous Fishes, by the inter-parietal. 
Or 
The Pre-sphenoidal Sclerotome. 
1. The centrum or basal part—the ‘ pre-sphenoid'.’ 
N.B. This element, distinct and normal in the Mammalia, is high and com- 
pressed in Birds. It is not ossified, as a rule, in the Reptilia, but, according 
to Goodsir, forms part of the bony septum of the ‘os en ceinture’ in Snakes 
and Frogs: it has no distinct osseous representative in Fishes ; the interorbital 
septum in this latter class being an orbito-pre-sphenoid. 
. The infero-lateral elements—the ‘ orbito-sphenoids.’ 
N.B. These elements—usually well-developed in the Mammalia, but extremely 
feeble in the Mole—are short and connate in Birds even when they have 
a distinct osseous centre*, which is not always the case. In the Chelonia, 
Crocodilia, and Lacertilia they are fibro-cartilaginous, and appear to have no 
centre of their own in the Opbidia and Batrachia.' They are generally 
unossified in Fishes. 
. The supero-lateral elements—the ‘ post-frontals.’ 
N.B. These elements are exogenous in Mammals, and, with one or two rare excep- 
tions, they are not distinct in Birds. They are well deveioped in Crocodiles, 
bo 
oo 
' In our description of the pre-sphenoid we have followed Professor Goodsir (op. cit. p. 154); if, however, 
Cuvier, Hallman and Huxley be tight, not only the detached ossifications anterior to the ‘hinge,’ but also the 
upper and anterior portion of the great inter-orbital ossification, is essentially ethmoidal in its nature. 
* Dr. Hallman (Die Vergleichende Osteologie des Schlifenbeins, Pl. I. fig. 2) represents the Goose as having 
a distinct V-shaped osseous centre for the orbito-sphenoids. In the African Ostrich there is one large osseous 
centre, an ‘orbito-pre-sphenoid’ exactly as in the Carp; whilst in the young Emen of the sixth week after 
hatching, the posterior margin of the orbito-pre-sphenoidal cartilage is already ossified,—a condition precisely 
like what is seen in the half-grown Pike. Recent observations on Birds scarcely mature have yielded us a 
distinct osseus pre-sphenoid, with exogenous orbital alee, in very many species: its absence is quite exceptional. 
