54 
In Amia the squamosal lodges three lateral sense organs, or 
sensory patches (No. 1). Two of these organs are innervated by 
branches of the ramus oticus facialis, and the third one by a branch 
of that lateral nerve that issues from the skull with the nervus glosso- 
pharyngeus. The two organs that are innervated by the facialis lie 
anterior to the point where the main infraorbital canal is joined by 
the dorsal end of the preoperculo-mandibular canal. The third organ 
lies posterior to that point. 
In Scomber, as in Amia, there are, in the squamosal, three lateral 
sense organs. Two of these organs are innervated by branches of the 
oticus facialis, and the third by a branch that has its apparent origin 
from the first vagus nerve. This latter branch is, almost unquestion- 
ably, the homologue of that branch of the nervus lineae lateralis of 
Scyllium or Salmo, described by HALLER, to which I made reference in 
my latest publication (No. 5, p. 377), and which I there considered 
as the probable homologue of the so-called dorsal branch of the 
glossopharyngeus of Amia. The two organs that are innervated by 
the facialis lie, in Scomber, as in Amia, in front of the point where 
the main infraorbital canal is joined by the preoperculo-mandibular 
canal, the third organ lying posterior to that point. 
That part of the squamosal of Scomber that lodges the lateral 
canal by which the bone is traversed, is a tall thin ridge or process 
of bone that looks like a separate plate or piece applied by its 
edge to the dorso-lateral surface of the rest of the bone. It pro- 
jects dorso-laterally, and lies between the muscles that fill the tem- 
poral groove of the fish and the dilatator operculi muscle, which fills 
the dilatator groove. The bone does not cover any portion of the 
dorsal surface of either of the muscle-masses between which it lies, 
there being absolutely no superficial plate-like extension to this 
part of the bone. The primary part of the bone forms part of the 
floor of the temporal groove, part of the floor of the dilatator groove, 
part of the posterior surface of the skull, and a part of its lateral 
surface, this last surface of the bone containing the facet that receives 
the posterior articular head of the hyomandibular. The bone is 
traversed by the external semicircular canal of the ear, and, partly 
from its hind edge and partly from the corresponding edge of the 
dorsal, dermal part of the bone, a long pointed process projects 
backward and laterally, and gives insertion to a fascia that covers 
the external surface of the adjacent segment of the muscles of the 
trunk. The entire bone thus has three distinct components, the dorsal, 
ridge-like portion, arising in connection with the lateral canal by 
