436 ON SOME NEW TRILOBITES PROM BOWNING, N.S..W., 



the centre of each is a row of fine punctations not visible to the 

 unaided eye. The granulation of the thorax is not nearly so 

 marked as that of the buckler and pygidium ; but each pleura 

 beai-s two conspicuous granules, one on each extremity, the one 

 on the basal extremity helping as before stated to make the axial 

 grooves more marked. 



The pygidium is shorter than the cephalic shield, much 

 granulated, and sub-semicircular ; that is, if it be transversely 

 sected so as just to remove the part bearing the rudimentary 

 axis, the remainder forms a semicircle. Along the margin are 

 several (6 are visible with a lens) concentric, or nearly concentric 

 striae, similar in character to those on the pygidium of B. Partschi, 

 Barr. The ribs are thirteen in number, separated from each 

 other by well-defined sutures. The medial rib is a little wider 

 than the luiited width of the three adjoining ones on either side 

 of it at their junction with the rudimentary axis, and about as wide 

 as the other three together. The second from the medial rib is 

 very narrow. The length of the medial rib equals about Jths that 

 of the one (first) which runs by the side of the thorax. Each rib, 

 except the medial one, is traversed longitudinally by a central ridge, 

 and the medial one by two such ridges, one on each edge. Each 

 of these carries a row of tubercles of larger size and more regularly 

 placed than the others. In this feature the spines of the pleurae 

 of the thorax resemble the ribs of the i)ygidium. The number 

 visible with a lens in each row on the spines is 5, and on most of 

 the ribs of the pygidium about the same number. These tubercles 

 are plainer on the cast than on the fossil. The medial rib ter- 

 minates in a somewhat spear-shaped point, the shaft oblong. The 

 line of articulation of the pygidium with the thorax is straight. 

 The rudimentary axis may be ranked semicircular, rather convex, 

 its axial furrow visible. The whole pygidium is slightly convex. 



Dimensions — Head long ^ in. (4 mm. nearly). Thorax : axis 

 wide at 5th and 6th segments ^' in. (3'385 mm.). Length of six 

 segments attached to the pygidium equal to the width, and, as 5th 

 and 6th segments are each about twice as wide as the last segment 

 and wider than either of the posterior segments, it is probable that 



