418 On a new Ostracoderm from Canada. 



trunk, but smaller, arranged in rows to simulate fin-rays. 

 The large caudal fin (c), which is slightly excavated he- 

 hind, is invested with small shagreen-like granules, but also 

 seems to have been stiffened with some stout deeper rays, 

 which are conspicuous through this covering (rig. 1 a). 

 Within the lobe at the base of the caudal tin, especially on 

 the side shown in tig. 1 a, there are also traces of hour-glass- 

 shaped calcified hremal supports. 



On the matrix of the fossil, both above and below the 

 caudal region, there are slight brownish streaks continuing 

 the lines of the squamation. These are doubtless merely 

 mineral stains, produced by the circumstances of fossilization. 



Judging by the results of Dr. 'J'raquair's recent researches, 

 to which reference lias been made, tlie fossil now described 

 represents a fish-shaped organism related to Cej/halaspis, but 

 distinguished from that and all known allied genera by the 

 absence of a continuous head- shield. Dr. Traquair has 

 already shown that the dermal plates both of the Pteraspidians 

 and of the Cephalaspidians developed originally by the fusion 

 of shagreen granules. The shield now described in the 

 Canadiau fossil is therefore of the most primitive nature, 

 apparently only modified by the development of a solid rim 

 round each orbit. For this reason the specimen is of great 

 interest, because it shows that one of the earliest types of 

 Ostracoderm armour survived until the latter ])art of tiie 

 Devonian period. It has even further imj)ortance as being 

 the first example of an Ostracoderm in which traces of the 

 axial skeleton of the trunk have been detected. 



No fragments of armour resembling that displayed by this 

 fossil a|)pear to have been hitherto described. The animal 

 must thus be placed in a new genus, Euplianerops, defined 

 by the presence of the stout orbital rims, the regular squama- 

 tion of small deepened scales, the slenderness of the caudal 

 ridge-scales, and the apparent absence of other well-developed 

 ridge-scales. The species may be named longoivas and 

 characterized by the proportions of the caudal region and the 

 nature of the scale-ornament. The family of Euphaneropidte, 

 of which this is the first known genus and species, must be 

 referred either to the Osteostraci or to the Anaspida. It is 

 distinguished from the Ateleaspidge, Cephalaspidaj, and 

 Tremataspidas by the non-fusion of the tubercles forming 

 the head-shield. It almost certainly differs from the Bir- 

 keniidte in the absence of a lateral row of perforations at the 

 hinder end of the branchial chamber, though the actual 

 branchial opening has not yet been seen. 



