442 MR. W. C. WILLIAMSON ON THE MICROSCOPIC STRUCTURE OF THE 
upwards at an acute angle round the margin of the scale — especially on the two sides 
that are fixed in the soft integument — from one of which the section represented in 
the sketch (fig. 3) was made. These laminse are composed of a multitude of still more 
minute lamellae. They are perforated by a number of narrow parallel tubes Wg^th 
of an inch in diameter, the greater proportion of which ascend direct from the inferior 
surface to the region immediately under the ganoin, fig. 3 a ; hut in the anterior 
margin of the scale these tubes abandon the vertical and assume the horizontal one, 
or even descend obliquely (fig. 3 h), but always run at right angles to the plane of the 
laminae through which they pass. In the latter case, instead of terminating, like the 
vertical ones, immediately under the ganoin, they do so at the angles which the 
various lamellae make, when assuming the upward direction ; many of them even 
appearing to take their rise from the under surface of the ganoin, as at fig. 3 c; but 
in the latter case the tube was originally in the position of fig. 3 d, its orifice having 
been subsequently covered over by the formation of newer lamellae of bone and 
ganoin. 
At the two free margins of the scale which overlap the concealed borders of those 
behind them, the tubes ascend from the lower surface, as shown at fig. 5 h (which 
represents a similarly constructed scale of Seminotus rhombife?') . On reaching the 
ganoin these tubes become branched ; their ramifications spreading out in a very 
thin layer, which covers the outer surface of each of the ridge-like projections which 
form the upper boundary of the vertical osseous laminae. This layer consists of a 
substance alike distinct from the ganoin above and the true bony tissue below, and 
to which I propose to give the name of Kosmine (from Koafieiv, to adorn). It is much 
more dense in its structure than the true bone containing no lacunae (though these, 
as the case in the example before us, are often seen through it), but is always fur- 
nished with some arrangement or other of minute branching tubuli. This kosmine, 
which has hitherto been confounded with the ganoin, under the common name of 
“ enamel,” occurs so frequently as to constitute an important feature in many ganoid 
and other scales, and consequently requires to be distinguished from the transparent 
and almost structureless tissue to which I have limited the application of the term 
ganoin throughout this memoir. 
The exquisitely beautiful appearance produced by this distribution of the tubes in 
the scale under consideration, is shown in fig. 4 a, which represents the upper surface 
of that portion of the scale as seen through the transparent ganoin. The sharp tooth- 
like ridges presented in the vertical section, fig. 3 c, are here more highly magnified, 
and form parallel spaces, fig. 4 a, before reaching which, the tubes usually divide into 
two or three branches, which afterwards give off beautiful arborescent ramifications, 
reminding us of leafless trees in winter. These communicate freely with one another, 
by means of anastomosing loops, in the arches of which some of the small lateral 
twigs dilate into crescentic cavities, fig. 4 h. The branches of each tube are usually 
limited, in their distribution, to the one lamina to which it is destined, but some- 
