On Species o/" Ehadiuiclitliys //'om the Coal Measures. 243 



distortion. What remains of the caudal fin is much twisted, 

 and only presents us with a portion of its origin, but the rays 

 are seen to be delicate, and their articulations rather distant. 



A specimen from Lanarkshire, in the collection of the Geo- 

 logical Survey of Scotland, shows, lying in connection w^th a 

 heap of the characteristic scales, the impression of a portion 

 of the cranial buckler, and from this impression it is evident 

 that its surface was sculptured wdth tolerably coarse ridges 

 passing here and there into tubercles. The position of the 

 orbit is clearly shown, below which is found the left maxilla 

 seen from its inner surface, together with the impression of 

 the outer surface of the mandible. The oval margin of the 

 maxilla is set w4th conical teeth, small, indeed, in the speci- 

 men, but large enough considering the small size of the jaw. 

 The mandible is slender and tapering, sculptured with a few 

 comparatively coarse ridges, which, as usual, pass forwards, 

 and also obliquely upw^ards, meeting the dental margin at 

 very acute angles ; its teeth are not exhibited. Some broken 

 remains of the opercular bones are visible, but not in a con- 

 dition for description. Lastly, behind the mandible are 

 several confused bony rays, the remains of the pectoral fin ; 

 these are clearly unjointed, and show that w^e have here the 

 structure characteristic of Rhadinichthys, Pygopterns, etc., in 

 which the principal rays of the pectoral are unarticulated till 

 towards their terminations. 



Remarks. — Although the external sculpture of the scales of 

 Rhadinichthys monensis. resembles in general character that 

 which also occurs, in various modifications, in other of the 

 smaller species of the genus, yet it has a facies of its own, 

 and, once seen, can be easily again recognised. We must, 

 however, await the discovery of more perfect specimens, 

 before a complete description of the fish can be given. 



Geological Position and Localities. — Only from the coal 

 measures, in which it is widely distributed, but apparently not 

 very abundant. The original specimens were found by the Earl 

 of Enniskillen at Ehuabon, in North Wales ; it occurs also in 

 North Staffordshire (collection of Mr J. Ward), and in 

 Lanarkshire (collection of the Geological Survey of Scotland, 

 and of Dr Hunter, Braidwood). 



