352 RAMSAY H. TRAQUAIR ON THE 
band of obtuse teeth commences, and extends all the way along the internal 
aspect of that margin to the anterior extremity. These are at first closely 
and somewhat irregularly packed together, but as the anterior extremity of the 
bone is approached they become very small, and tend to be arranged in lines 
transverse or slightly oblique to the margin. Of the premaxilla I can say 
nothing. Of the palato-quadrate apparatus, the only element I have seen is a 
plate (fig. 12), evidently the representative of the large pterygoid or ectoptery- 
goid of the Paleeoniscidee, which I found lying detached on a slab of shale 
beside a maxilla (fig. 13) and numerous scales of Hurynotus; portions of the 
same bone, crushed and obscured, are often seen in the heads of entire specimens. 
It carries a large oval patch of obtuse teeth, this patch showing three slight 
longitudinal elevations, separated by two corresponding shallow depressions. 
Of these elevations or ridges, two form the margins of the tooth patch, one of 
them corresponding with the external margin of the entire bone at this place ; 
the third passes midway between them, and bears the largest teeth. The 
teeth themselves are all obtuse, often at the first glance suggesting an 
ageregation of small grains of shot. On examination they are seen to be 
mostly in the form of short blunt cones, sometimes round in transverse 
section, or somewhat elliptical, or polygonal from close crowding; on the 
dentary element of the mandible they are frequently laterally compressed in 
shape. The base is sometimes, though not always, slightly constricted, and a 
few slight vertical grooves commonly extend some distance up the sides. 
Microscopically they consist of dentine, traversed by delicate tubules radiating 
from a basal pulp cavity, and surmounted by a cap of structureless “enamel” 
corresponding to, but relatively much larger than, that of the teeth of 
Palzoniscide and many other ganoids. It is apparently the wearing down, by 
attrition, of this enamel-cap, and the consequent exposure of the softer dentine 
below, that gives the flattened tops of such worn teeth (fig. 15) the “ dimpled” 
aspect referred to by Hucu Miiier in his letter to Sir Paine Grey-EcErron. 
The orbit (07) is placed right above the middle of the maxilla, and in its 
boundary shows at least two conspicuous suborbitals (s.0). One of these is a 
narrow curved bone forming the posterior-inferior part of the orbital margin, 
and is joined in front by another (the so-called “lachrymal”) of a larger 
size and broader shape, forming the anterior-inferior orbital boundary, and 
extending along the anterior part of the upper margin of the maxilla towards 
the snout. 
The operculum (op) is small and of a quadrate shape, with the posterior- 
superior and anterior-inferior angles rounded off. Immediately below it is 
another plate (¢.op), somewhat larger and higher, whose posterior-inferior angle — 
is quite rounded off, while the anterior-inferior comes close behind the quadrate 
articulation of the mandible. This is evidently the exact homologue of the 
