98 RAMSAY H. TRAQUAIR’S 
margins display a few denticulations—4 to 5 on the largest flank scales, 
diminishing to 2 or 3 in those further back. The most remarkable feature in 
this form is, however, the very small development of the low narrow ventral 
scales, which are so conspicuous in the preceding. Such scales are indeed 
distinguishable along the ventral margin between the pectoral and anal fins, 
but on the other hand, in the abdominal region as many as eight scales may 
be counted down from the lateral line without any prominent change in form 
taking place. 
Remarks.—This is by far the most common fish in the Eskdale beds, 
and from the comparatively large number of specimens before me, has 
admitted of a very full description, nevertheless there are difficulties in the 
way of its satisfactory determination as a species. 
In 1877, I described, under the name of Rhadinichthys Geikiei, a small 
fish from the Wardie Shales near Colinton, Mid-Lothian, from specimens, 
which unfortunately were mostly fragmentary or distorted, save one very small 
one, which I considered to be a young individual of the species. These 
specimens, so far as they go, show a fish of much the same proportions as 
the above described form from Eskdale; the markings on the head bones, 
where visible, are very similar; so is the scale ornament, though perhaps 
the ridges are a little finer, and the denticulations of the posterior margin 
rather more numerous in proportion to the size of the scale. None of the 
larger specimens show the ventral region, save one, in which a similar 
arrangement of low narrow scales exists, though not so conspicuously, and 
the absence of this feature in the smaller examples is paralleled by the condition 
found in those from Eskdale, which I have felt obliged to consider only as 
young forms, or at most as a variety (elegantulus). On the whole, after 
most careful comparison of every scrap from both localities, I cannot find any 
very tangible or decisive mark of specific distinction, and therefore, although I 
may possibly be hereafter proved to be in error, I do not feel justified in 
separating the common Rhadinichthys of Eskdale from Rhadinichthys Getkiet. 
Again, it is possible to point out scales on the flanks of many Eskdale 
specimens of Rhadinichthys Geikiet which are indistinguishable from those of 
the Coal Measure Rhadinichthys monensis, Egerton. This isolated fact, 
however, cannot prove the identity of the two species unless corroborated by 
the discovery of more perfect examples of Rhadinichthys monensis, which is 
as yet only known from scattered scales, and very fragmentary specimens 
indeed. What I have seen of the latter certainly inclines me to believe in the 
distinctness of the two forms, and the similarity of certain scales is of constant 
occurrence in closely allied species of Palzeoniscidee. 
Position and Locality.-- Near Glencartholm, Eskdale, in the Cement-stone 
croup of the Calciferous Sandstone series. 
