On the Microscopic Structure of the Scale of Amia Calva. 95 
characteristic and unlike ordinary lacune, d with its elongate and 
more tapering form and fewer canaliculi is assuming a more 
normal appearance, ande is still more normal, having altogether 
lost its short abrupt lateral branches, and only presenting very 
fine and tapering terminal ones. At the margin of the scale we 
find lacunze of this kind alone (fig. 5), differing from each other 
only in respect of their length, number and extent of canaliculi, 
&c., and reminding us of the well known lacunez of the allied 
Lepidosteus osseus (fig. 6) which are figured in most books 
on microscopy. They differ from them, however, in being much 
larger, less globular, and having much wider canaliculi which do 
not anastomose to the same extent; whilst the scale itself does 
not exhibit any of the canals running in from the surface which 
seem to be constant in the scales of Lepidosteus. There do not 
appear to be any lacunz in the posterior part of the scale from 
about cd backwards, in front of this line they begin as small 
simple forms like e, fig. 4, and a, fig. 5. 
EXPLANATION OF THE PLATES. 
Fig. 1. Entire scale of Amia calva magnified 5 diameters, showing the finely toothed 
posterior edge, the general direction of the ridges, and the position of the characteristic 
lacune. The line a b indicates the place where the ridges tend to run into each other, 
cd the level behind which no lacune are found. 
Fig. 2. A portion of the posterior part of the scale showing the nature of the ridges 
and the toothed border, x90. The arrows show the direction in which the light came, 
oblique illumination having been used. 
Fig. 3. Lacune from the central part of the scale, x180. At ais seen one in which 
the central lacuna is linear; 5 is one of the highly complex forms; c and d have smaller 
lacunar systems connected with them. 
Fig. 4. Lacune occurring in the same field of view, x 260. Taken from a part of the 
scale about half way between the centre and the margin; a, b,c, are of the characteristic 
complex form, d and e are simple. 
Fig. 5. Lacune from the marginal part of the scale, X260. Atais seen one of the 
simplest forms. 
Fig. 6. Lacune from the scale of Lepidosteus osseus, 260 showing the small size of 
the lacuna, their globular shape and very fine canaliculi. 
The drawings were all made under a Wollaston camera lucida. 
