of Edinburgh , Session 1877-78. 
659 
is produced upwards and backwards in a long slender process. The 
scales are comparatively thin and very large, sometimes, as noticed 
by Hibbert, attaining a diameter of 5 inches ; usually they occur in 
a broken condition. Their attached surface is marked by a central 
boss and concentric lines of growth. The outer surface, very rarely 
seen, is ornamented by closely set granules, which towards the 
posterior border of the exposed area are confluent into wavy ridges 
terminating in the margin. These seem certainly to be the scales 
attributed to R. Hibberti by M‘Coy, but not by Young ; they are 
probably also the same as the undescribed ‘ Phyllolepsis tenuissimus ' 
of Agassiz. 
R. Hibberti occurs throughout the Cementstone and Carboniferous 
Limestone series of Scotland, the most noted locality being Gilmerton, 
near Edinburgh. 
2. R. ornatus , sp. nov. Traquair. 
To this species, which seems never to have attained anything like 
the dimensions of R. Hibberti , belong the specimen showing the 
pectoral fin described by the author in 1 87 5, the head described by 
Mr L. C. Miall, and in fact nearly all the specimens in which any 
portion of a fish with bones or scales in situ is shown. The orna- 
ment of the cranial bones is somewhat similar in character to that 
in R. Hibberti , but very much coarser ; the same is the case with 
the bones of the shoulder. Of the bones the following have been 
recognised by the author — dentary , operculum , principal jugular , 
clavicle , infra-davicular ; there are also others whose determination 
is still somewhat doubtful. The clavicle differs somewhat in form 
from that of R. Hibberti, its lower portion being narrower from 
before backwards. The expanded portion of the infra-clavicular is 
also shorter than in the larger species, but the same slender process 
is sent backwards and upwards from its posterior superior angle. 
The pectoral fin is subacutely lobate. The scales are thicker than 
those of R. Hibberti. The exposed area of the external surface is 
marked with short, interrupted, wavy, reticulating ridges, whose 
direction is mainly parallel with the posterior border of the scale ; 
in the interval between these, more delicate ridges are seen radiating 
from the centre. It is apparently on a scale of this species that Dr 
Young has founded his description of those of R. Hibberti. 
