94 Mr. H. W. Mackintosh, 



narrow groove (a, a, 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 lacunae 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 lacunae 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 lacunae, not connected at 

 all with the central lacuna but merely overlying it. As a rule 

 there is not much tendency to communication amongst the 

 different lacunae ; 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 often 

 (d, fig. 3 ; a, 6, 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 lacunae 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 

 m the same field of view, whilst a, b, and c are eminently 



