1280 



NEW YORK STATE MUSEUM 



pertain, into the other. The more strongly marked or by 

 analogy the dorsal surface carries a narrow median eleva- 

 tion running from the blunt end to near the acute ex- 

 tremity; it becomes continuously more obscure toward this 

 end and may there fail to cause any interruption of the 

 surface. The more complete of these specimens carries about 

 55 transverse segments, others carry from 40-50 accord- 

 ing to the degree of their completeness. These segmental di- 

 visions are produced by oblique depressions departing from the 

 axial line of the body, bending forward toward the 

 margins but over the median and anterior parts becom- 

 ing more transverse. These depressions bound the surfaces 

 of oblique overlapping plates directed backward or toward the 

 blunt extremity of the body. The plates appear to be continuous 

 across the full width of the body but are narrowest at the axial 

 line and broader outward, their fore and aft width apparently 

 being at about half the distance between the axis and the outer 

 margin. Their edges are frequently broken off in detachment 

 and the posterior plates appear to be longer and hotter defined 

 than the others. 



These plates (if they are correctly thus interpreted) are rather 

 narrower than similar structures in living species so far as our 

 observation has extended and yet it is not clear to us what part 

 of their actual width has been concealed by their oblique direc- 

 tion into the matrix. The overlap is on the anterior surface of 

 each plate and the projecting posterior edge could not have been 

 greatly extended. Construing the structure thus given from a 

 relief of the natural dorsal mold Ave note in addition to the midrib 

 a low submarginal ridge on each side which anteriorly impresses 

 the segments in such a way as to thicken each but posteriorly 

 produces only a* '^sinuosity in the outline of the plates which is 

 doubtless intensified by the breaking away of ilie edges of the 

 plates themselves. Besides these there are obscure traces of 

 other Longitudinal lines. The posterior extremity of the body is 

 blunt but the anterior end tapers narrowly and in some of the 

 specimens terminates in a smooth blunt subcylimlric process 

 which resembles what the head should apparently be in such an 

 organism. 



