102 F. R. Cowper Reed — Trilobites, Haverfordwest. 



species. In shape it is broadly parabolic ; the axis is conical, convex^ 

 about one-third the width of the pygidium in front, is not enclosed 

 by a furrow behind, but sinks down rather suddenly to the general 

 level of the lateral lobes in the postaxial piece ; there are three 

 distinct narrow rings on the front part of the axis, followed by 

 lateral traces of a fourth ; the posterior end of the axis is elevated 

 into a blunt tubercle. The axial furrows converge posteriorly to 

 a little behind the axis and then curve gently outwards. The 

 lateral lobes are flat, horizontally extended, and consist of three 

 pairs of pleurae, each well-defined and traversed by a diagonal 

 furrow of equal strength, but only the first two pairs of pleurae 

 end in free points beyond the margin, the third pair not interrupting 

 the regular rounded outline of the posterior edge of the pygidium. 

 The free ends of the second pair, which are alone preserved in our 

 specimen, project as short, broad, slightly recurved points. The 

 postaxial piece, which is broad, appears not to be marked off 

 posteriorly from the third pair of pleurae, the limiting furrows 

 dying out before reaching the margin. The surface of the pygidium 

 is uniformly tuberculated. There is a wide concentrically striated 

 fascia on the inferior surface, extending inwards nearly to the tip 

 of the axis. 



Dimensions. 



mm. 



Length 14 



"Width (about) 18 



Affinities. — The figure given by Schmidt ' of a pygidium which 

 he attributes to L. depressus, Angelin,- resembles this specimen in 

 general characters, and particularly in its rounded posterior outline 

 and in the short free points of the two first pairs of pleuree, the third 

 pair ending within the margin. But the axis is not of the same shape, 

 and has only two rings on it. Schmidt also states that he is doubtful 

 about the characters of the posterior portion, and it may not have 

 a rounded outline behind the second pleurae. Angelin's figure 

 certainly does not convey the same impression. But Z. offinis, Ang.,^ 

 and Z. conformis, Ang.,* in spite of being more pointed behind, are 

 undoubtedly the nearest allies, the shape of the axis, number of 

 segments, posterior tubercle, lateral lobes, pleurae and furrows 

 agreeing much more closely than any others; and without any 

 hesitation I assign this Slade form to this group which has been 

 called MelopolichasJ' A form from the Keisley Limestone has been 

 referred by the present author® to Z. affinis on the strength of 

 some pygidia and a head-shield, and another to a variety of 

 L. conformis. 



1 Schmidt: Eev. Ostbalt. Silur. Trilob., pt. ii (1885), p. 95, pi. iv, fig. 4. 



2 Angelin: Pal. Scand. (1854), p. 70, pi. xxxtI, fig. 4«> 

 ^ Ibid., pi. xxxviii, fig. 4 J. 



* Ibid., pi. xxxviii, fig. 5. 



6 Eeed: Q.J.G.S., vol. h-iii (1902), p. 73. 



6 Eeed: Q.J.G.S., vol. lu (1896), p. 427. 



