218 JOURNAL OF COMPARATIVE NEUROLOGY. 
does it show any vestige of the frontal commissure as given for 
Chaetostomus and Clarias by PoLLarp. 
b. The Infra-orbital Canal. This canal, after its separa- 
tion from the supra-orbital, runs forward and outward for a 
short distance still enclosed in the frontal bone. No sense 
organ is contained in this portion of the canal. It then enters 
the last (7th.) bone of the suborbital series. In this bone there 
is neither sense organ nor pore, nor is there a pore between it 
and the frontal bone. The seventh and last pore of this canal 
lies between the sixth and seventh suborbital bones and the re- - 
mainder of the canal passes through six suborbital bones (most- 
ly very slender, mere drain-pipe bones to support the canal) all 
of which are separated by dermal tubes and surface pores and 
each of which bears a single sense organ. Following McMur- 
RICH (’84, p. 278), I reckon the lachrymal (his adnasal) as the 
first bone of the suborbital series. 
All of the organs of the infra-orbital canal, as well as ad- 
jacent small pit organs are innervated by the r. buccalis, which 
also supplies the row of large pit organs running transversely 
in the vicinity of the anterior nasal aperture. Fig. 1 gives the 
arrangement of these latter sense organs, which have been pre- 
viously mentioned by ALLis (’97, p. 629) as occurring in 
Ameiurus catus and Silurus glanis. 
c. The operculo-mandibular canal. In the specimen figured 
this canal does not communicate with the other canals of the 
head but is independent for its entire extent. It begins at the 
tip of the mandible with a pore situated a little laterally and in 
front of the mental barblet. It immediately enters a canal in 
the dentary bone, within which there are four sensory organs, 
all separated by dermal tubules, the fifth tubule running out 
between the dentary and articular bones. The latter bone con- 
tains one sense organ and no pore, though there is a pore im- 
mediately behind it. The canal at once enters the preoper- 
culum and here bears three organs, all separated by pores, and 
terminates by a pore at the caudal end of the preoperculum. 
The operculo-mandibular canal is accompanied by a row of large 
pit organs which, like the canal organs, are innervated from the 
