No. 436.] APPENDAGES OE TREAT ATA S PIS. 



lateral edges and partly overs it. In all probability the 

 lar and other organs, which it lias covered, were in the sar 

 sheltered on both sides b v similar plates. It is narrow, eloi 

 by degrees tapering and ending bluntly. The surface is 

 same glossy lustre as the other portions of the exoskelet* 

 is covered with ridges which have a nearly parallel di" 

 and continue without interruption. On the interior surfac 

 I, Fig. 12) which is quite smooth, are seen the polygonal 

 tion lines of the vacuole walls, and the openings of the 

 canals. There is no evidence that it has consisted of mc 

 one plate, nor that the supposed extremity has been cov< 

 several plates, as the limbs of Fterichthys." Lindstron 

 not attempt to justify his conclusion that the structure in 

 tion is an appendage, or to indicate its point of attachme- 

 the effect such a discovery, if confirmed, must have on the 

 fication of the Ostracoderms. The importance of Linds 

 discovery is somewhat diminished by the fact that what he 

 an appendage is but a single plate. Hence it is unc 



whether it was part of a scale or spine paired or unpaired ' 

 ing either to the head or trunk. 



the British Museum indicates that the so-called latera 

 openings are better explained as points for the attachme- 

 oar-like appendages, and that the projecting processes some' 

 attached to the openings should be regarded, not as a port : 

 the matrix squeezed out of the orbits, but as either the rem 

 of an appendage itself, or as the matrix that originally fille 

 base of the appendage. 



In view of the common bonds of relationship that unit- 

 various groups of the Ostracoderms, and in view of the pre 



