250 
ORIGINAL ARTICLES. 
thermore, below the gap which lay between the two trabeculae, and 
beneath the posterior half of the median prolongation of these tra¬ 
beculae which has been described, there lay a long and narrow piece 
of bone, exhibiting on the upper side of its anterior half a toler¬ 
ably strongly projecting keel, which fitted into the groove of that 
median cartilaginous part. Posteriorly, however, it divided itself into 
two pointed crura, which diverged at a very acute angle and applied 
themselves closely to the under side of the bony investment of the 
notochord; and somewhat behind its middle it sent off laterally two 
tolerably long and narrow alee, which attached themselves to 
the lower side of the two cartilaginous trabeculae. The oral mucous 
membrane passed over the under side of the whole bone, but was 
only loosely connected with it; whence it could be easily stripped off 
from the bone, which, on the other hand, was very firmly connected 
with the cartilaginous part of the basis cranii. 
The bone in question represented the presphenoid. Just in front of 
it there was a much smaller bone which lay on the under side of the 
median prolongation of the two trabeculae cranii, so that it was placed 
between this and the oral mucous membrane. It had the form of a 
thin, narrow, pointed, irregularly triangular plate, and had its pointed 
end directed backwards, its broader and somewhat thicker end for¬ 
wards. The maxilla and premaxilla were in contact with the anterior 
end of this plate, which was the vomer. The alse or lateral parts of 
the sphenoid, which still consisted almost entirely of cartilage, 
formed a continuous whole, neither with the body of the sphenoid, 
nor with the trabeculae cranii. On the other hand, the exoccipitals 
appeared as immediate prolongations of the cartilaginous noto¬ 
chordal investment, but were already ossified to a certain extent. 
In other embryos, which were almost ready to leave the parent, 
the vomer and the body of the sphenoid were more developed, 
and were very similar to those of adult Blennies. The basi-occipital 
had also greatly increased at the expense of the cartilaginous border 
which surrounded it in younger embryos; so that, of the border 
itself, only the anterior part was present, though tolerably broad. The 
bony matter had also increased immediately round the cephalic part 
of the notochord, and appeared as a true though magnified cast of it. 
Only indistinct traces were left of that part of the notochord. The 
trabeculae had partly disappeared : at least, in many embryos which 
I examined with reference to this point, I could no longer find 
their middle part, but I could only observe that the cartilaginous 
border of the basi-occipital was produced into two short cartilagi¬ 
nous points, forwards, and the coalesced part of the trabeculae into two 
somewhat larger and also quite symmetrical points, backwards. This 
coalesced part, still entirely cartilaginous, was however larger in 
all its dimensions than in younger embryos, and had sent off, imme¬ 
diately behind the olfactory organs, between which it lay, two short, 
moderately thick, outwardly directed processes, which supported the 
anterior end of the olfactory nerves. In adult Blennies, on the 
