454 ALLIS. [Vor XIV. 
its dorsal surface, is then naturally explamed. Ii has been 
caught between the two parts of the bone before they fused. 
In Gymmarchus niloticus the nasal sense-organ bone is still 
found as a separate bone, and is described by Erdl (No. 13) as 
bone No. 4 It forms, m Gymnarchus, a direct, anterior con- 
tinuation of the infraorbital cham of bones, lymg imtercalated 
between the most anterior of those bones and the premaxillary 
bone. The latter bone has a short palatal plate, but no other 
process of any kind. The infraorbital bones are said by Endl 
to be half canals, and they undoubtedly partly enclose an imfra- 
orbital lateral canal, although that canal is not described. The 
nose is thus, apparently, in the adult of Gymaarchus niloticus, 
simply the most anterior organ of the main infraorbital, lateral 
line, just as it seems im a measure to be in larvae of Amia (No. 
I, PPp- 520, 531, 537) and of Necturus (No. 20, p. 492; PL 
XXXVIII, Fig. 1). Bone 3 of Gymnarchus is too evidently 
the nasal bone to need any comment. Bone 7, which is called 
by Erdl the nasal, seems to be a purely dermal, piscime 
ethmoid. 
The bone that forms m connection with the nasal lateral 
sense organ, in fishes other than Amia and Gymnarchus, I can- 
not recognize as a separate bone in any descriptions at my dis- 
posal,? unless it be, as already stated, m bone 2 of Esox. The 
1 Smee my manuscript was sent to the publishers I have received three of 
Broom’s Works - Ce ee ee ee 
Premaniilary,” Proc. Linx. Soc, N. S. Wales, Vol X, Pt Ill, 1895; «On the 
Occurrence ee ee Prevomer in Gomphognathus.~ Joxrn. Anat. 
& Péyzs, VA. XXXL NS. Vol XI, 1897; and “On an Apparently Hithato 
Undesctibed Nasal Floor Bone im the Hazy Ammadillo.” Jourz. Anat. & Pigs, 
Vol XXXII, N-S, Vol XI, 1897- In the frst of these three publications Broom 
States his conclusion that the palate process of the premaxillary of mammals is the 
homologue of the damb-bell-shaped bone of Omithorbynchus, of the vomer of 
Reptile. etc. and he proposes for all these bomes the mame prevomer. He states 
that J. T. Wilson, before him, bad recognized the womerine character of the damb- 
bellchaped bone, and om pege 433 of his own work he bricfly summarizes the mam 
arguments advamced by that author m support of his conclusions. If they be 
consulted, it will readily be seen that they all apply with equal force to the posterior 
process of the premaxillary of Amia, which bone is thus possibly the piscine homo- 
logue of the dumbbell shaped bone of Ornithorhynchus, and im that case, if Broom 
is correct, the homologue also of the palatime process of the premaxillary bone. It 
is, however, certainly not the homologue of the socalled vomers of Polypterus, 
which are generally considered as the homologues of the vomers of Amphibia, if 
