GRIFFITHIDES. 37 



extremities being faceted and obtusely pointed. Pygidium composed of from 

 twelve to fifteen^ coalesced segments ; axis strongly arched and ribbed like 

 the thorax, but no ornamentation visible ; side lobes of pygidium also arched ; 

 the ribs running to the border ; a wide striated margin is exposed where 

 decorticated. 



Formation. — Carboniferous Limestone. 



Locality. — Carnteel, Tyrone, Ireland. 



I was formerly of the same opinion as my friend Prof. Morris that GrijffltJiides 

 longisjpinus of Portlock was identical with the G. longiceps of the same author, and 

 this opinion was also shared by V. von Moller ; but, having been favoured with the 

 opportunity of examining Portlock's original specimens of both these forms, I have 

 satisfied myself that they are entitled to be kept distinct. 



In G. longispinus the small raised cheeks are covered with rather large bead- 

 like tubercles ; the glabella is longer in proportion, and has a few scattered 

 tubercles on the surface ; the neck-lobe is narrow. 



In G. longiceps the head-shield is finely granulated, the neck-lobe is broad, the 

 basal lobes are larger, and only one tubercle marks the centre of each. The 

 thoracic segments are more strongly arched in G. longispinus, and the pygidium is 

 composed of more somites than in G. longiceps, and is more elongated and more 

 highly arched than in the latter. 



I think a comparison of our figures of G. longiceps (Plate VI, figs. 7 and 8) 

 with those of G. longispinus (Plate VII, figs. 5 a, h, c, and 6) will satisfactorily 

 show all the points in which these two species resemble and differ from one 

 another. 



Subjoined we give Portlock's original description of his Griffitliides longispinus, 

 ' Report on the Geology of Londonderry,' &c., p. 312, 1843 : 



" This beautiful species approximates to G. longiceps, as the specimen figured 

 in pi. xi, fig, 9, is imperfect, and may, therefore, have had lateral spines ; 

 there are, however, some good marks of distinction, the glabella is not quite so 

 long nor so narrow, and the pygidium is rather longer, has fifteen axal segments, 

 and is smooth, whilst the thoracic segments are granulated ; these may, however, 

 be only in part accidental variations from peculiar circumstances, wear, &c. The 

 glabella is gibbous, and longer than in G. globiceps. The wings [free cheeks] pass 

 anteriorly under or in front of the glabella, and are prolonged backwards in long, 

 flat, striated spines (see magnified view, pi. xxiv, fig. 12 h). Though the 

 granulations are well marked on the thoracic segments (pi. xxiv, fig. 12 e) none 

 are visible in this specimen on the pygidium (fig. 12 c) ; when decorticated a large 

 striated and nearly vertical margin appears, as in fig. 12 d, which also shows that 

 the under surface does not exhibit the extension of the segments to the margin 

 1 The extremity is injured so that the exact number cannot now be ascertained. 



