130 GANOID FISllKS OF THE CARBONIFEROUS FORMATION. 



the foregoing, but the cranial roof-bones ornamented with closely set ridges, which are 

 j)roj)ortionately somewhat coarser and more contorted in their arrangement; in one very 

 perfect sj)ecimen, in which the head-bones are beautifully exhibited (PI. XXX, figs. 7, 

 8), the maxilla is destitute of tuberculation along its inferior margin. The scales are but 

 faintly marked, those on the sides (fig. 10) and belly, as well as those towards the tail 

 (fig. 11), being nearly smooth; their posterior margins display a few denticulations — 

 four to five on the largest flank-scales, diminishing to two or three in those further back. 

 The scales on the na[)e of the neck (fig. 9) are, as in the typical form, strongly striated. 

 The most reniarkable feature in this form is, however, tiie very small development of the 

 low narrow ventral scales which ai-e so conspicuous in the preceding. Such scales are, 

 indeed, distinguishable along the ventral margin between the i)ectoral and anal fins, but 

 on the other hand, on the abdominal region as many as eight scales may be counted 

 down from the lateral line without any prominent change of form taking place. 



Geological Posilion and Localitij. — Rare in the Calciferous Sandstone Series at 

 Glencartholm, Eskdale. The specimen here figured is in the Collection of the Geological 

 Survey of Scotland. 



C. Variety iklicaluhns, Traqiuiir. TIate XXX, figs. 12 — 15. 



Descriplion. — Length from \\ to 3| inches ; shape and general proportions as in the 

 typical form. 



The bones of the head and shoulder-girdle (fig. 13) are externally sculptured with 

 delicate ridges, which, although they follow the same general pattern as in the typical 

 form, show less tendency to contortion and interruption, and except along the dentary 

 margin of the maxilla, are nowhere seen to break up into tubercles. The scales (figs. 14, 

 15) are proportionately thinner, and those of the front part of the body have their upper 

 and lower margins rather straightev and more parallel with the long axis of the body, 

 but the same arrangement of low narrow scales is seen along the bellv. The vertical 

 grooves along the anterior margin of the sculptured area of the scales are almost lost, 

 nearly the whole surface being covered witli minute sharp ridges and furrows, which, 

 with the exception of one or two which run parallel with, and close to, the inferior 

 margin, are directed rather diagonally across the scale, ending on the denticulations of 

 the hinder border; sometimes two of these ridges terminate on one denticulation. 

 Finally, this delicate ornament is in most cases continued back to the scales of the tail- 

 pedicle itself. The fins are similar in position, shape, and structure to those of the 

 ty])ical form, but comparing specimens of the same size, their rays seem to be rather 

 more delicate and more distinctly articulated. 



Geological Posilion and Locality. — Rare in the Glencartholm fish-beds belonging to 

 the Calciferous Sandstone Series. The specimen figured is in the Collection of the 

 Geological Survey of Scotland. 



