438 
MR. W. C. WILLIAMSON ON THE MICROSCOPIC STRUCTURE OF THE 
exceedingly thin lamellee*, which are folded back upon themselves at the edges of 
the scale, the lowermost ones overlapping those which' rested upon them, and cover- 
ing them over to a considerable extent. This is especially the case at the anterior 
portion of the scale, but also exists to a considerable extent at the lateral margins, or 
those which are parallel to the mesial line. Fig. 2 represents the section of the half 
of a scale taken at right angles to this line, and where along the whole of the upper 
margin we see this duplicature of the lamellae towards the centre of the scale. It is 
also seen to a slight extent along its anterior border. 
Between these parallel lamellae are multitudes of lacunae with radiating canaliculi. 
These lacunae M. Agassiz designates by the almost exploded term of “ bone-cor- 
puscles.” They appear to be cavities between two contiguous lamellae, in the plane 
of which the canaliculi are spread out, but without appearing to perforate either of 
them. 1 have not attempted to represent them in the Plate, as they would have 
rendered its details confused and indefinite. 
Along the upper margin of the section, especially at certain points, as at fig. 2 a, 
the terminations of several of these lamellae combine to form a tooth-like projection, 
each of which corresponds with more clearly marked divisions existing in the section 
of the scale, and which I have distinguished as constituting the Lamince ; were not 
these surmounted by ganoin-f', they would have formed elevated ridges on the surface 
of the scale. 
Arranged nearly at right angles to the lamellae, are a number of narrow tubes, 
figs. 1 y'and 2 b. These penetrate from the exterior to the interior of the scale, and 
have usually a diameter of about g^^th of an inch. They are of nearly uniform 
width, somewhat undulating, and though usually simple, sometimes divide into two 
or three branches. A few of them terminate in the inferior and middle lamellae of 
the scale, but in the central and anterior regions, they are generally prolonged until 
reaching within a short distance from the upper surface. At the anterior part, and 
towards the lateral margins, they terminate in the region where the successive lamellae 
turn back upon themselves, figs. 1 c and 2 c. Thus the scale is divided into two por- 
tions ; a superior one, in which all these tubes, preserving their rectangular position in 
relation to the lamellae through which they pass, enter from the upper surface, and an 
inferior and far more extensively developed one, which is wholly supplied from below. 
At their termination these tubes generally divide into two or three short branches. 
They were seen by M. Agassiz, but on some points our observations differ. He says 
* I have employed the terms lamellae and laminae throughout the memoir to represent two distinct appearances. 
The former I have applied to the ultimate thin layers into which the use of high magnifying powers enables us 
to subdivide the thickness of the scale. By the latter I have distinguished certain more conspicuous subdivi- 
sions, each consisting of numerous lamellae, and each of which is thought by M. Agassiz to be the result of 
one year’s growth. 
t 1 have preferred employing the term Ganoin, to represent the hyaline substance covering over many of 
these scales, in preference to that of Enamel. It is different in its character from the prismatic structure covering 
the dentine of the teeth of mammals, and the employment of one term to designate both leads to error. 
