Carboniferous Trilohites. 77 



jn the dorsal furrows of the glabella just in front of tlie eyes, 

 have been observed by McCoy, Oldham, Salter, Barrande, Von 

 Moller, and Woodward. 



McCoy (Synopsis of the Silurian Fossils of Ii-eland, 1840, p. 

 43), thinks that these auxiliary impressions occupy jnst the po- 

 sition which the antennas would have occupied, and that anten- 

 nae, being hollow organs, would leave a hole in the external in- 

 tegument if broken oif. 



Capt. Portlock (Rep. Geol. Londonderry, &c., 1843, p. 261), 

 noticed them in his description of Amjjyx Sarsii without remark. 



Dr. Oldham (Jour. Geol. Soc. Dublin, 1846, Vol. 3, p. 189), 

 in his description of Griffithides glohiceps, says: — '"In the fur- 

 rows which separate the cheeks and glabella, about halfway be- 

 tween the front of the eye and the anterior margin, I have ob- 

 served in all the t(^lerably preserved specimens which I have seen, 

 a small hole or indentation" ; but he does not offer an explana- 

 tion of their use. 



In 1847, Mr. J. W. Salter (Quart. Jour. Geol. Soc. London, 

 Vol. 3, p. 251), in his article on the structure of Trinucleus, re- 

 fers to tlie discovery by himself and Dr. Emmrich, of the facial 

 suture in Trinncleus ornatits, and states that its course "is ob- 

 liquely upwards from the eye-tubercle to the upper end of the 

 glabella, where it appears to terminate in a solitary deep perfo- 

 ration, similar to those which surround the head." This is the 

 first observation of these organs, that we know of, in the genus 

 Trinucleus. 



Later on, in 1852, Barrande (Systeme Silurian de la Boheme, 

 Vol. 1, p. 230), refers to the observations of McCoy, and also to 

 various genera on which he has observed auxiliary impressions. 

 He remarks : '' When the shell exists, as we have seen it in spe- 

 cimens of Calymene Baylei, etc., it is bent inwards, as a funnel 

 shaped depression. We have thought that this bending inward 

 of the shell was simply designed to afford points of attachment 

 for the muscles of the jaws, and that they have the same origin, 

 as the similar indentations which we have indicated in the pleu- 

 i-aB of various species of trilobites, * * * * /^^ fragment of 

 Cheirurns gihhuf^, broken along the line of the dorsal groove and 

 the length of the glabella, exposing to view one of the alae of the 

 hypostoma in sifAi, shows that this wing of the hjpostoraa fits at 



