94 Mr. H. W. MAcKINTOSH, 
narrow groove (4a, 4, a, fig. 2), and bearing on their upper surface 
a broad flat elevation, the middle of which is again raised up 
into a sharp narrow ridge. The lacunz whose form I wish 
specially to call attention to are grouped together in the middle 
line near the anterior edge of the scale, and appear as minute 
black dots visible to the unassisted eye on careful scrutiny. 
They are placed immediately beneath the superficial layer of 
ganoin which clothes the whole surface of the scale, and apparently 
makes up the entire of the posterior thin part, which is altogether 
devoid of lacunz of any sort. When examined under a low 
power (180 diams.) they are seen (fig. 3) to consist of a central 
axis which for the most part has a decidedly fusiform shape, 
but which sometimes (a, fig. 3) is simply linear. From this 
central axis arise a number of very short canaliculi, which are 
mostly linear and end abruptly, but sometimes taper rapidly to 
a very fine point. Starting from these, in some cases, and super- 
posed on them in others, are other canaliculi, which lying thickly 
together often give the lacuna to which they belong a wonder- 
fully confused appearance (6, fig. 3), and may even render it a 
matter of some difficulty to trace the central axis. It must be 
understood, however, that in many cases like b, fig. 3, the apparent 
canaliculi are really small independent lacunz, not connected at 
all with the central lacuna but merely overlying it. Asa rule 
there is not much tendency to communication amongst the 
different lacunze ; sometimes (c, d, fig. 3) we find a small lacuna 
or a system of them in slight connexion with a larger one, though 
I have not been able to satisfy myself that this is always a true 
anastomotic union. Employing a higher power (260 diams., fig. 4) 
we bring out more clearly the fusiform shape of the main lacuna, 
and the usually abrupt termination of the canaliculi. Very otten 
(d, fig. 3; a, b, fig. 4) these are placed with singular regularity, 
forming a series of crosses with the points of intersection at the 
lacuna, giving the entire system an appearance which is unique 
so far as I can ascertain. These are the only lacunz found at 
the centre of the scale, but as we go out towards the margin we 
find others making their appearance, more in accordance with the 
usual form. Thus in fig. 4, which represents a group occurring 
in the same field of view, whilst a, b, and ¢ are eminently 
