GRIFFITHIDES. 83 



I had certainly no intention of burdening the list of Carboniferous Limestone 

 Trilobites with another species, and I had, in fact, placed figs. 2, 10, and 11, PI. 

 VI, provisionally under G. gloldceps ; but on a more detailed examination of the 

 original of fig. 10, it occurred to me something more might be made out by deve- 

 loping it further. To my surprise two long spines were uncovered, and I then 

 perceived that figs. 2 and 11 had at one time also possessed cheek-spines, but these 

 have since been broken off. G. glohiceps, on the contrary, has blunt and short 

 cheek-spines, large basal lobes to the glabella, and the portion of the test preserved 

 shows the head-shield to have been finely punctate, whereas in G. acanthiceps the 

 surface of the head- shield is distinctly granulated. 



The discovery of the detached head with the long cheek-spine of this species, 

 proving it to be distinct from G. globiceps, led me to a further and closer exami- 

 nation among the remaining doubtful specimens, and one belonging to Mr. J. 

 Aitken, having been skilfully developed by our (Brit. Mus.) Mason, Mr. C. Barlow, 

 revealed the same character of the head as in the specimen from the Woodwardian 

 Museum, and in addition exposed the thorax and abdomen very fairly preserved, 

 enabling me to complete the description of G. acanthiceps (see PI. VII, fig. 2). 



Another specimen, also from Cambridge, exhibiting a detached head and 

 pygidium upon the same piece of matrix, is drawn (on PI. VII fig. 3). 



11. Geiffithides longiceps, PortlocJi, 1843. PL VI, figs. 7, 8, and 9. 



Geiffithides longiceps, Portlock. Eep. Geol. Londonderry, p. 310, t. xi, figs. 



7 a, h, 1843. 



— — M'Coy. Synopsis Carb. Foss. Ireland, p. 160, 1844. 



— — Morris {in part). Cat, Brit. Foss., p. 109, 1854. 



— — R. Woodw. {in part). Cat. Brit. Foss. Crust., p. 37, 1877. 



General form ovate-oblong ; head-shield very large in proportion to the rest of 

 the body, forming two fifths of the entire length; glabella very gibbous, pyriform, 

 basal lobes obtusely triangular, with a tubercle on the centre of each ; fixed cheeks 

 very narrow, but expanding rather at the sides of the glabella in front of the eyes ; 

 axal portion of the neck-lobe very broad, and separated by a strong furrow, and 

 bearing one tubercle on its centre ; eyes moderately large, reniform, surface very 

 finely faceted; raised inner portion of free cheek rather narrow, surface finely 

 granulated, outer margin wide, posterior angles produced into broad and stout 

 spines, reaching to the fifth segment of the thorax ; thorax composed of nine free 

 segments, the axis arched, equalling half the entire breadth of the thorax ; each 

 segment bordered by ten or eleven granules on its axis along the posterior border, 

 and seven or eight on each pleura ; pleurae rounded at their extremities, pygidium 



