446 CARBONIFEROUS TRILOBITES OF AUSTRALIA 



one inch: widtli, half an inch; cephalon, one-quarter inch: thorax 

 and pygidiuH), each three-eighths of an inch. 



In the proportions of length to width, and the character of 

 the pvgidial granulation, this trilobite agrees with P. gemmu- 

 lifera Phillips, with which it also agrees in the equality of the 

 lengths of the thorax and pygidium. In other specific features, 

 thev differ. In the cephalons and pygidia of F. collinsi and F. 

 truncdtuld, there is much common to the two. They agree in 

 possessing narrow, straight-sided and tul)erculate glabella, eyes 

 close to the axial furrows, and similarly tuberculated pygidia: 

 but the tuberculation on the glabella of the former is much more 

 pronounced than it is on the latter, and the sinuate course of the 

 anterior branches of the facial sutures of the latter is more pro- 

 nounced than that of the former. Thepj^gidium of F truncatula 

 has seventeen or eighteen annulations in the axis, and fourteen 

 divisions in each pleura ; but in F. collinsi^ these parts 

 number fourteen (or thirteen and a terminal piece), and ten 

 respectively. In the former, the pygidium has no border, and 

 the pleural ribs extend to the periphery; on the other hand, the 

 latter species has a very distinct pygidial border, which, except 

 in the case of the anterior pairs, the pleural ribs do not cross. 

 The tubercles of the pygidial axis of the former are arranged in 

 longitudinal rows; this is not quite so with those of the latter. 

 Of the North American Phillipsif^, the nearest relative to ours 

 appears to be P. insignis, which apparently has the same number 

 of divisions in the axis and pleurae of the pygidium, as are in 

 the similar parts of P. collinsi. The tuberculation of the axial 

 rings is much alike in the two species. In other respects, they 

 differ rather widely. The only Australian Carboniferous trilobite 

 fragments bearing any resemblance to P. collinsi are two pygidia 

 described and figured, but not named, by Mr. Etheridge, Junr.* 

 The one pygidium he placed in the genus FhiUipsia {loc. cit., PI. 

 xxii., fig. 14). It agrees with F. collinsi in possessing fourteen 

 rings in the pygidial axis, and in having a tuberculate test; but 

 differs in having a continuous, smooth, flattened border, and 



'" R. Etheridge, Junr., Mem. Geol. 8urv. N. 8. Wales, Pal. No.5, Pt. ii., 

 1892, pp. 129-130, PI. xxii., figs. 14, 15. 



