352 Mr. T. P. Barkas on Ctenoptychius. 
1874, 1875, and 1876, copies of which papers were forwarded to 
the Geological Society of London, Professors Owen, Huxley, 
Traquair, Etheridge, Marsh, Messrs. Davies, Atthey, Ward, 
and several other paleontologists, and are the only papers 
extant in which the minute microscopical structures of the 
teeth of Coal-measure fishes are given with great elaboration 
and detail, accompanied ‘by ninety-four admirably drawn en- 
raved figures. 
This work Mr. Stock appears not to have seen, or he would 
not have said that “a microscopic examination would help 
to settle the point ” in reference to the fish or labyrinthodont 
origin of the alleged ‘ Kammplatten.”’ 
My son, Dr. W. J. Barkas (who is now in Australia), in 
the papers above referred to, describes at length and with great 
accuracy and minuteness the microscopical structures of Cteno- 
ptychius pectinatus, C. denticulatus, and C. apicalis, and 
finally, for various substantial reasons, transfers C. apicalis 
to the Petalodi. 
He then proceeds to describe Ctenoptychius unilateralis as 
follows (and this passage I quote verbatim) :— 
“ OCtenoptychius unilateralis was first described and figured 
by Mr. T. P. Barkas, F.G.S., in the ‘ Geological Magazine’ 
for January 1869. It is very rare, but not so much so as C. 
apicalis ; and, so far as I know, it has only been discovered 
in these measures. 
“Tt differs externally from all the preceding varieties with 
respect to the position of the base, which is situated on 
one side of the crown instead of at the lower border. The 
specimen from which fig. xvi. was drawn is a very typical 
tooth, and is about the average size, though I possess some 
measuring less than half the length. ‘The teeth having this 
peculiar lateral base vary much im form; but whether these 
varieties belong to one fish, though situated in different parts 
of its mouth, or pertain to distinctly different fishes, I cannot 
say. The tooth was classified among the Ctenoptychit on 
account of the resemblance between the external characters 
of its crown and those of the crown of C. pectinatus ; for if a 
short base had been attached to the interior border of the 
crown of C,. wnilateralis instead of to the side, it would have 
closely resembled the former tooth; the serrations, however, 
are not quite so deep in this new variety. 
“The crown is separated from the base on the external 
surface by a vertical concavity, and on the internal by a pro- 
minent ridge; the base exceeds the crown in length, and 
gradually tapers to a point as it proceeds outwards; but 
the latter is the higher of the two parts. ........... 
