360 RAMSAY H. TRAQUAIR ON THE 
powerfully heterocercal and inequilobate caudal, a dorsal high in front and 
becoming fringe-like posteriorly, and an anal similar in form but considerably 
shorter in the extent of its base. There is also clear evidence of its well- 
developed and abdominally placed ventrals, a fact also alluded to by Sir Pumie 
Grey-Ecerton in his description, so that it is difficult to understand how 
Dr Youne, in his paper on “ Platysomus and Allied Genera,” has described 
Eurysomus as being deficient in that member. The scales seem to be somewhat 
more strongly keeled than in Mesolepis, nevertheless, as Professor Youne 
observes, “ the scale character allies it somewhat to the latter genus.” 
The specimen preserved in the Edinburgh Museum (Plate IV. fig. 10) is 
deficient as regards the top of the head, nevertheless it shows several details of 
the greatest importance. There is a large clavicle, similar in shape to that of 
Eurynotus and Mesolepis, in front of which is a broad interoperculum, having 
below it a number of narrow branchiostegal rays. All these bones are orna- 
mented externally by somewhat coarse crenulated wavy ridges passing into 
tubercles. But the points of greatest interest are those concerning the con- 
figuration of the jaws, and here the resemblance to Mesolepis is brought out 
in a manner still more remarkable. In front there is a beak-like portion of 
bone (p. mz), convex and smooth externally, and evidently praemaxillary in its 
nature ; its lower margin is injured, and here the roots of several broken-off 
teeth are visible. Behind this is the left maxilla (mz), which is narrow in front, 
but broadening out behind in a sort of angular spatulate manner; its broad 
posterior portion is covered behind by a tubercular ornament. Its upper 
margin is nearly straight, and slopes gently downwards and forwards; the 
posterior margin, gently convex, slopes also downwards and forwards, but at a 
less inclination than the superior one, with which it forms an acute angle above, 
while below it forms an obtuse angle with the lower margin, which is concave, 
and passes on to the lower margin of the premaxilla. No teeth are perceptible 
in the maxilla when looked at from the outside, but just below the left mandible 
we get a view of what is clearly the inner aspect of the anterior part of the 
maxilla of the opposite side (mzx’), but crushed out of its place, and this dis- 
plays a row of broken-off tooth-stumps. The mandible (mm) is not completely 
exhibited, being largely overlapped above and behind by the posterior-inferior 
angle of the maxilla, but its similarity in general form to that of Mesolepis is 
obvious. It is comparatively short and stout, pointed in front and broad 
behind ; a wide oblique shallow groove marks off the dentary margin. The 
exposed portion of the oral margin bears a row of the large characteristic 
pedunculated and flattened teeth (fig. 11) so well described by Sir Pxitip 
GREY-EGERTON. But there is a second or inner row of mandibular teeth, and 
these would seem to be borne upon the splenial element, judging from the 
anterior portion of the opposite mandibular ramus (mn' fig. 10), which, seen 
