DEVELOPMENT OF THE SKULL IN THE SALMON. 
99 
plates (Traquair, Journ. Anat. and Phys. vol. v. figs. 1, 2, 3, 7, na.) ; these are sup- 
plemented by an additional pair (na'.). The nasal sac itself has a small roof-bone, 
lettered o.t. (os terminate) in Dr. Traquair’s figure. In Muller’s figure of Polypterus , 
as quoted by Huxley, op. cit. p. 22, the main superethmoidal plates are lettered N. It 
is evident, therefore, that there are several candidates in the Polypterus for homology with 
the human nasal bones. In the Pishes generally I retain the term “ nasal” for the “ os 
terminate” (the so-called “ turbinal” of Owen), which is the foremost of the upper fork 
of the “ lateral-line” series of mucous bones, and which covers the nasal sac. This bone 
is shown in the Salmon in Plate VI. fig. I, n. ; it belongs to the same category as the 
superorbital (s.o.b.). These investments of the nasal region have merely to be regarded 
as a commencing specialization of the dermal scutes in relation to more and more meta- 
morphosed ethmoidal structures. 
Two large splints, one very large, invest the basis cranii ; one of these has been known 
for many centuries in its mammalian form ; it is the vomer (Plate VII. fig. 2, v.). This is 
an oblong bar of bone, thick in front ; it sends upwards a sharp keel on this anterior 
portion, between the halves of the ethmoid (Plate VII. fig. 5, v.) ; behind, it is carinate 
downwards (Plate VII. fig. 7), and it is armed with sharp recurved teeth. This bone 
underlies the next for a considerable distance (Plate VII. figs. 2, 7, 8, v., pa.s.). The next 
bone, by its primordial condition, characterizes the Ganoid and Teleostean Fishes and the 
Amphibia, although I find few even of the higher Vertebrata without traces of it; it is 
largest in the lower Ganoids, for instance the Sturgeon. A good Ichthyopsidan name 
was first given to it, “ parasphenoid,” by Professor ITuxley (see Elem. p. 170); it is a 
submucous bone, intimately related to the basis cranii, and is of great length (see Plate 
VII. figs. 2 & 4, pa.s). This bone is large, a long leaf, with descending laminae, and is 
split in front. It is also split behind into several snags, and from its hinder third 
sends upwards “ basitemporal wings.” It is upwardly keeled in front, downwardly keeled 
behind, and flattened in the middle (see sections, Plate VII. fig. 7-11, Sc Plate VIII. 
figs. 4-6, pa.s.). A view of the basis cranii after these two parastoses have been removed 
(Plate VIII. fig. 2) is instructive as to their architectural value. 
The lateral-line series does not give us any conspicuous “ supratemporals ;” but there 
is one attached to the “pterotic” which is worth description; it is shown in Plate VI. 
fig. 1, s.t. This curved, rod-shaped mucous bone is articulated below to a large falcate 
bone full of gland-burrows, but this is formed in the proximal part of the opercular 
fold ; it is the “ prseopercular hence it is evident that the slime-canals do not confine 
themselves to the two forks of the lateral-line series. 
1 Over the eye there is one “superorbital,” and under the eye two thirds of a ring of 
“suborbitals” (Plate A I. fig. 1, s.o.b., su.o .); these are thick and strong-rimmed where 
they contain the glands, thin and splintery at the outer edge. The suborbitals are 
developed in the superior edge of the subocular bar, external to the cartilage. 
The bones of the upper jaw show the aberrant or subtypical character of the Salmon, 
the maxillary being dentigerous as well as the intermaxillary. The latter (Plate AT. 
