714 SILURIAX TRILOBITES, 



Obs. — -The glaljella of this species is veiy similar to that of 

 C. longisjmia, Mitchell {Acidaspis longispinis, Mitchell), but here 

 the specific resemblance of the two species ceases. The cephalon 

 of C. Jackii has a greater proportionate width, and its spined free 

 cheeks, shorter and slender occipital, genal and pleural spines, and 

 the very different anterior pleural spines clearly separate it from 

 the former. 



From 0. Vogdesi it is so different that comparison is needless. 

 For the same reason we need not enter into any explanation to 

 differentiate it from C. Verneuili and C. vesiculosa, Barr. From 

 C. Dufrenoyi it is distinguished by the much less quadrate out- 

 line of the cephalon in that species, nor does this species possess 

 the expanded anterior lateral portions (free cheeks) of C. Jackii. 

 The same feature also distinguishes it from G. inira, Barr., and in 

 addition also the highly pedunculated eye of the last named is a 

 strongly differentiating character. On the other hand like C. 

 Jackii, Barrande's species possesses the peculiar swimmeret- 

 like spines on the thoracic pleura?. Lastly, in C, Prevosti 

 these spines are replaced by short simple ones, whilst the pro- 

 portions of the cephalon entirely disagree with those of C. Jackii. 



Named in honour of Mr. R. L. Jack, Government Geologist of 

 Queensland, who collected the specimens. 



Log. and Horizon. — Bathurst Road, near Bowning, Co. Harden, 

 Middle Trilobite Bed — Bowning Series ( = Hume Beds, Jenkins, 

 and Yass Beds, Jyaxid) — ^Wenlock. Coll. — Geological Survey of 

 Queensland, Brisbane; and Mitchell. • . 



Ceratocephala niPEDiTA, sp.nov. ' 



(PL Liii., figs. 11-13.) 



Sp. Char. — Body and cephalon in a complete form unknown. 

 Glabella highly tumid, tuberculated throughout; central lobe very 

 intensely arched transversely and longitudinally, long, narrow, 

 much higher than the cheeks or lateral glabella lobes, much com- 

 pressed laterally just behind the frontal expansions, which are 

 very distinct, narrow and each sui'mounted by two distinct 

 tubercles. Median and basal joairs of lateral glabella lobes only 



