from the Neighbourhood of Edinburgh. 265 
a slight notch on the posterior margin, and are evidently 
obliquely perforated by the lateral slime-canal. 
Towards the dorsal and ventral margins the scales get 
considerably lower than on the flanks. ‘Those represented in 
fig. 5 (also magnified two diameters) are from a situation 
further to the front of the fish than those from which fig. 3 
was taken—namely, from the belly, a little distance behind and 
below the suboperculum. In them the articular spine is very 
broad and triangular, arising from the entire upper margin of 
the scale, and showing besides a few peculiar grooves on the 
surface, radiating from the middle of the base. 
The foregoing description of the configuration of the scales 
has, together with the illustrative drawings, been principally 
taken from impressions left on the hard ironstone after very 
careful removal of the friable osseous matter, and from accurate 
“ squeezes” in modelling-wax taken from the same. 
Conclusion.—F rom the foregoing description it is at once evi- 
dent that the little fish just described belongs to the Paleeozoic 
section of Dr. Young’s suborder of Lepidopleuride ; but it can 
hardly be included in any previously described genus. Neces- 
sarily leaving dentition out of consideration, the shape of the 
body and the relations of the dorsal fin alone widely distinguish 
it from Mesolepis and Amphicentrum. From Platysomus it is 
also separated by the form of the head, with its short blunt 
snout and relatively more anteriorly placed orbit, as well as 
by the nature of the scale-ornament, which in all the described 
species of Platysomus consists of fine vertical or slightly 
diagonal ridges or striz. In the typical Platysomi too (e. g. 
Pl. gibbosus, striatus) “the dorsal fin commences at the cu/- 
minating point of the dorsal ridge, and extends thence to the 
upper lobe of the caudal fin, the component rays diminishing 
very gradually in length from first to last ;” moreover it con- 
tains “from 80 to 100 fin-rays”’*; here, on the other hand, 
the dorsal fin commences very much behind the highest point 
of the back and contains considerably fewer rays, though their 
exact number is not ascertainable. There only remains the 
very imperfectly known genus Cleithrolepis, Egerton}, from 
beds of doubtful Carboniferous age in New South Wales, and 
which, to certain points of resemblance to Platysomus, adds 
the peculiarity of having a homocercal tail; this organ, being 
absent in our specimen, is not available as a means of compa- 
rison. Although the rounded figure and posteriorly arising 
dorsal fin of Clecthrolepis, added to Sir Philip Egerton’s state- 
* Sir Philip Egerton, in ‘ Quart. Journ. Geol. Soc. London,’ 1864, xx. 
3 
“+ Loe. cit, p. 3, and pl. i. figs. 2 & 3, 
