492 SILURIAN TRILOBITES OF NEW SOUTH WALES, vi., 



Crotalocephalus SCULPTUS. 

 (Plate XXV., tigs.4-8). 



Obs. — Several heads of Crotalocephalus have come under our 

 notice, which disagree with the species above described in 

 having the frontal lobe of the glabella very much larger and 

 more anteriorly produced. The glabella-furrows appear more 

 acutely V-shaped, but, in other respects, they agree with our C. 

 silverdalensis. 



A portion of a similar cephalon was figured by Mr. Charles 

 Jenkins,* and, associated with this cephalon, occur portions of 

 pygidia, and of a thorax consisting of four conjoined somites. 

 These pvgidial fragments agree, in the character of their struc- 

 ture, with each other. The chief features of the thoracic frag- 

 ments are: — (1) the axis is exceedingly prominent, strongly 

 arched transversely, and forward: (2) axial furrows deep; (3) 

 pleura? deeply incised by the oblique furrows, and the distal ends 

 of the anterior portions of the segments intensely tuberculate, 

 as are also the fulcral parts; (4) pleural spines longer than the 

 pleurae, from which they subtend: (5) in the proportions of length 

 of the cephalon to width, across the neck ring, the two forms 

 materially differ. For instance, three cephalons of C. silverda- 

 lensis gave the following lengths and widths, respective!}' — 14 : 8, 

 25 :15, 35 : 21; and the only complete cephalon of C. sculptus 

 yielded 31 : 15 for the same parts. In the one case, the length 

 is much less than double the width, and, in the other, practi- 

 cally just double the width of the neck-ring. These difterences 

 lead us to give specific rank to the form. 



Log. and Hor. — Bowning Creek, Parish Bowning, County 

 Harden: Hume beds. Parish Warroo, County Murray (Jenkins;: 

 Lower Trilobite Beds. Upper Silurian. 



Ckotalockphalus ('?)sp. 

 A very fine cephalon, minus the free cheeks, has been brought 

 under our notice by Mr. C. Siissmilch, Principal of the Newcastle 

 Technical College, and collected by him from the Molong Lime- 



Jenkins, Proc. Linn. Soc. N. 8. Wales, iii., Pt.l, 1878, P1.6, fig.o. 



