72 CARBONIFEROUS TR1LOBITES. 



furrows before mentioned, close to the anterior margin of the cheeks, com- 

 municating with the interior. In T. seticomis they form two small circular punctse 

 within the margin ; they are in the same furrows, penetrate to the interior, and are 

 smaller than the punctures of the wings. In T. radiatus they hold the same 

 position as in T. Caractaci, that is, very close to the anterior margin of the cheeks. 

 They are rather larger in T. elongatus, in which they occupy the same position as 

 in T. Caractaci, but are smaller, and placed rather more within the margin. In 

 T. fimbriatus, though small, they are very conspicuous, being about the size of 

 one of the punctures of the margin of the shield, and their own diameter within 

 the margin. It is very remarkable that those organs are most obvious in what are 

 considered blind Trilobites ; whether it may be as a compensation for the want of 

 eyes that they are furnished with better-developed antennas, organs seeming so 

 mysteriously to combine in themselves the exercise of all the senses, besides their 

 own aeroscepsin, as Lehmann calls it, I am unable to conjecture." 



He adds "that these punctures exist, although very much reduced, in 

 Trilobites with eyes, I have also ascertained, as they are found, although exceed- 

 ingly minute, in the common Griffithides globiceps of the Carboniferous Limestone, 

 holding the same position as in the other genera alluded to, being seated in the 

 same furrows, but farther back from the anterior margin." 



Dr. T. Oldham, F.R.S., in the ' Journ. Geol. Soc.,' Dublin, 1846 (vol. hi, part 3, 

 p. 189), writes in his description of Griffithides globiceps : " In the furrows which 

 separate the cheeks and glabella, about half way between the front of the eye and 

 the anterior margin, I have observed in all the tolerably preserved specimens which 

 I have seen, a small hole or indentation. These are constant and therefore 

 obviously connected with the structure of the creature, although I cannot offer an 

 explanation of their use. They are similar to those noticed by Portlock in his 

 Ampyx Sarsii" (op. cit., p. 261). 



In 1847, Mr. J. W. Salter communicated a paper to the Geological Society, 

 " On the Structure of Trinucleus, with remarks on the species " (' Quart. Journ. 

 Geol. Soc.,' 1847, vol. iii, pp. 251 — 254), in which he observes : " The peculiar 

 perforated border is the most interesting part of these animals, and I propose to 

 examine it critically. 



" The puncta are almost always arranged in radiating rows, three, four, or 

 more holes in each row, and these being at equal distances they form concentric 

 lines. In T. granulatus, two of these rows are separated by a furrow from the 

 rest ; in T. seticomis, three are distinct from the remaining two or three, by the 

 front rows being sunk in a deep concentric furrow. Other modifications take 

 place ; in T. fimbriatus, the two front rows are turned downwards ; lastly, in T. 

 ornatus — for by that name we must call T. Caractaci — the dots occur most 

 frequently in quincunx order, i.e. the radiant rows appear zigzag and not direct; 



