APPENDIX, 



Note on the Nature of Certain Pores Observable in the Cephalon or 

 Head-shield op some Trilobites. (Plates IV and IX.) 



Among the numerous specimens of Carboniferous Trilobites which I have had 

 the opportunity to examine during the last three years, many examples exhibit a 

 peculiarity of structure which had already arrested the notice of such keen 

 observers as Portlock, M'Coy, Oldham, Salter, Barrande, and Valerian von Moller. 

 I allude to certain pores more or less well-marked, and placed usually one on either 

 side of the glabella in the axal furrow, and upon the facial suture which separates 

 the free-cheek from the fixed one, forming the margin of the glabella, and just in 

 front of the compound eyes (see Plate IV, figs. 6, 8 and 10, p. 22). 



In working at the Silurian Trilobites Professor F. M'Coy, in his ' Synopsis of 

 the Silurian Fossils of Ireland, collected by Sir Richard Griffith ' (Dublin, 1846, 

 4to, p. 43), writes, "I have observed in several Trilobites a peculiar pore situated 

 in the furrow which separates the glabella from the cheeks near the anterior 

 margin on each side, which seems to have escaped general notice, and which it is 

 not impossible may be the remains of setaceous external antennas." Professor 

 M'Coy thinks these pores occupy just the position which the antennas would have 

 occupied, and that antennas, being hollow organs, would leave a hole in the 

 external integument if broken off. He then proceeds to observe that "in Ampyx 

 these punctures are extremely remarkable and obvious, and it is only in this group 

 that they have, to my knowledge, been observed by naturalists. Captain Portlock 1 

 having noticed them, but without any remark, in the description of his A. Sarsii. 

 They are to be seen, but not exactly in the right place, in his figure of that fossil, 

 in which they form two very deep, oblong punctures, communicating with the 

 interior ; they are situated in the furrow before-mentioned, about their own length 

 within (or posterior to) the anterior margin. I have likewise observed them in all 

 the species of the genus Trinucleus. In T. Caractaci they form two rather large 

 circular punctures, as large as one of the punctures of the wings ; they are in the 



1 • Eeport on the Geology of the County of Londonderry, and of parts of Tyrone and Fermanagh ' 

 (Dublin, 1843), p. 261. 



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