74 CARBONIFEROUS TRILOBITES. 



funnel-shaped opening nearly 2 mm. in diameter in the head of Cheirurus 

 claviger" l 



" When the shell exists, as we have seen it in specimens of Galymene Baylei, 

 Cheirurus gibbus, &c, it is bent inwards, as a funnel-shaped depression. We 

 have thought that this bending inwards of the shell was simply designed to afford 

 points of attachment for the muscles of the jaws, and that they had the same 

 origin as the similar indentations which we have indicated in the pleurae of various 

 species of Trilobites. We have observed the conformity of the position of these 

 pits in the depression of the axial furrows of the thorax as in the head. We 

 recall again the indentations of the shell on the glabellal furrows and on those of 

 the axis of the pygidium in Dalmannia. 



" We were satisfied with these analogies, and we sought no other explanation 

 for these little indentations. But after having read the opinion of Prof. M'Coy, 

 we have studied all the specimens afresh which might serve to elucidate this 

 question, and we have found a portion of a Cheirurus gibbus, which seems to 

 explain the matter satisfactorily to our views. This fragment is broken along the 

 line of the dorsal groove and the length of the glabella, exposing to view one of 

 the alse of the hypostome in situ. This wing of the hypostome fits at its extremity 

 to the interior of the little funnel-shaped projection formed upon the underside of 

 the head-shield. These details are very distinct, owing to the very perfect 

 preservation of this specimen with its shell. After this we cannot accept any 

 other interpretation for the genus Cheirurus than that which we have given. We 

 leave to savans the task of pointing out the value of these analogies, and they 

 may be able to apply this method of explanation to other genera mentioned by 

 Prof. M'Coy" {op.cit, p. 230). 



Valerian von Moller, in his paper (" Ueber die Trilobiten der Steinkohlen- 

 formation des Urals ") contributed to the ' Bulletin de la Societe Imperiale des 

 Naturalists de Moscou," 1867, p. 44, notices these same pores in the head of 

 Phillijjsia Eichwaldi as "very distinct deep funnel-shaped openings, which run a 

 little obliquely and enter into the underside of the cephalothorax." He cites the 

 opinion of M'Coy and of Barrande, and says, in conclusion, " I quite agree with 

 the observations of Barrande, and I feel sure the more one examines these 

 indentations the more one feels satisfied that they are only superficial openings." 



I have carefully examined these puncta in the Carboniferous Trilobites, and 

 have sought for some satisfactory explanation in various other members of the 

 class Crustacea, both recent and fossil. 



1 This is not shown in Barrande's figures of Cheirurus claviger, pi. 40, figs. 1 — 12, nor in 

 Ch. gibbas, figs. 35 — 39, but is seen in pi. 41, fig. 17 ; it is also well shown in Trinucleus ornata, pi. 29, 

 figs. 1 — 8, and in Placoparia Zippei, pi. 29, figs. 30 — 34, and in Galymene Baylei, pi. 43, fig. 49, and in 

 many others not referred to by Barrande. 



