55 
which it is traversed; the body of the bone, of perichondrial or endo- 
chondrial origin, and lodging the external semicircular canal; and the 
posterior process, formed in connection with the fibrous structures to 
which it gives insertion. The body of the bone has the same relations 
to the skull of the fish that Sagement found in the corresponding part 
of the bones of the Teleosts he examined, and it is certainly their 
equivalent; while the dorsal ridge, or process, of the bone is the 
equivalent of the dorsal, horizontal, dermal portion of the bones in 
those other Teleosts. This dorsal ridge in Scomber is also the equi- 
valent of the entire bone of Amia, as SAGEMEHL describes that bone, 
but it would seem as if the V-shaped process along the ventral sur- 
face of the lateral edge of the bone in Amia might, contrary to 
SAGEMEHL’S determination, represent of the perichondrial body of the 
bone of Scomber and other Teleosts, and not a part of the dermal 
component. 
In Polypterus the so-called parietal of Traquatr’s (No. 32) de- 
scriptions is said by him to be traversed by the main lateral canal small 
of each side of the head. Because of this relation to the canal VAN 
WHE (No. 36, p. 259) concluded that the bone could not be a true 
parietal, and that it must be formed by the fusion of the squamosal 
and parietal elements of the skull of the fish. He accordingly 
proposed for it the name squamoso-parietal, a proposition to which 
PoLLARD later gave his adhesion (No. 26, p. 407). It is to be noted, 
however, that the so-called squamosal part of this bone takes little, 
if any, part in the formation of the articular facet for the hyoman- 
dibular. According to TRAQUAIR the anterior part of the lateral edge 
of the bone lies mesial to the spiracular canal, the posterior part 
forming the dorsal portion of the hyomandibular facet. According 
to POLLARD’s figures, where the bones are shown in section, the dorsal 
end of the hyomandibular is capped by what he calls the third spira- 
cular ossicle, and it is that ossicle and not the hyomandibular itself 
that articulates with the lateral edge of the squamoso-parietal. Both 
the ossicle and the anterior portion of the dorsal end of the hyoman- 
dibular are said to lie internal to the spiracular canal. The squamoso- 
parietal also comes into no relation whatever with the external semi- 
circular canal of the ear, that canal traversing the so-called opisthotic 
of the fish. Of this latter bone TRAQUAIR says (No. 32, p. 168): 
“This bone, the ‘mastoid’ of Acassız and MÜLLER, I must identify as 
the opisthotic of HuxLeyv, but it is evident that it also includes his 
epiotic element”. It seems to me that it must include not only those 
two elements, which are, respectively, the intercalar and exoccipitale 
