452 



PEOF. P. M. DUNCAN ON SOME 



divided upper arm-plate suggests, according to Ljungman, the 

 alliance with Ojjhiolepis. It is not without affinities to OpJiio- 

 glypTia, but it differs materially and genericallj from the new form 

 described above. 



Ophiogltpha steiata, sp. nov. Plate IX. figs. 4, 5, 5«. 



An Ojpliiog'lijplia with strisB on the proximal side margin of 

 the side arm-plates. 



The disk is pentagonal, thick, flat above, straight and high in 

 the interbrachial spaces, strongly notched for the arms ; and the 

 numerous scales are flat, overlaj)ping, and inconspicuous. The 

 central scale is large, and is surrounded by five small ones, suc- 

 ceeded by five large and some small scales, the rosette being indi- 

 stinct. A medium-sized scale separates the radial shields at their 

 inner angle ; numerous scales pass towards the interbrachial space, 

 where there is a central line of large ones bounded by two rows 

 of smaller scales. 



The radial shields, small and irregular in shape, are separated 

 within, are then united for a short space, and are parted externally 

 by the long convex uppei* arm-plate, which is friuged with a row of 

 rudimentary spines at the sides. Sunken at the edges, the shields, 

 about as long as broad, are bounded aborally by a straight or by 

 a curved edge, into which the large radial plate fits on either side. 

 In young specimens a small j)late occurs, besides the first arm- 

 plate in relation to the radial shields, and fills up the angle more 

 or less ; but with growth this becomes an important plate, and is 

 not then distinguishable from the first arm-plate. 



The radial plates are rounded, large, tall from below upwards on 

 the side of the arm, broad above and narrow below, where they 

 seem to merge into the generative plates. They form a conspicuous 

 part of the interbrachial space, and are armed with about fifteen 

 short sj^ines, which are sharp and distinct above, and which unite 

 and form broad expansions below. 



The convex upper arm-plate, the rounded radial plates, and the 

 colour (a faint grey) of the radial shields renders the parts over 

 the insertion of the arms very remarkable. 



The mouth-shields are large, occupy nearly all the space below 

 and between the arms, and even are bent upwards slightly at the 

 lower part of the tall interbrachial sp)ace ; they are longer than 

 broad, broadest and roundly curved aborally, narrower and more 

 sharply curved orally, where there is a slight point, and the sides 



