540 Dr. H. Woodward—On the Pores in Trilobites. 
stome 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 
Steinkohlenformation des Urals’) contributed to the “ Bulletin de 
la Société Impériale des Naturalistes de Moscou,” 1867, p. 44, 
notices these same pores in the head of Phillipsia Hichwaldi as “ very 
distinct deep funnel-shaped openings which run a little obliquely 
and enter into the underside of the cephalothorax.” He cites the 
opinions of M‘Coy and of Barrande, and says in conclusion, “1 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. 
And first I] would observe, in reference to the varied forms of 
Trinucleus, with corrugated, punctate, perforate, and serrated margins, 
to the head-shield, that we may see in the larval “‘ King Crab” or 
_“Horse-shoe Crab” (Limulus polyphemus) of North America, just 
before hatching, that the head-shield retains indications, in the well- 
marked fimbriated hepatic lobes, of the presence of a once divided 
border, corresponding with the five or six distinct cephalic somites. 
This fimbriated margin to the cephalic shield, seen in the young of 
Limulus, is observable also in the head-shield of Hemiaspis limuloides, 
from the Lower Ludlow of Shropshire. As to the explanation given 
by M. Barrande for the series of depressions, or invaginations, of the 
crust, of various Trilobites which are seen to correspond with each 
thoracic somite, and are placed exactly in the depression of the 
furrow on each side of the dorsal axis and are even observable in 
the axial furrows of the pygidium of Dalmannia, we agree with him 
entirely, and there can be, I think, no doubt whatever that they are 
perfectly homologous with the similar pits or indentations of the 
crust, observable in the thoracico-abdominal shield of Limulus, which 
give rise to six powerful calcareous processes within (apodemata, 
Milne Edwards; entapophyses, Owen), for the attachment of the 
muscles required for the locomotory organs. 
But whether the two pits, or pores, placed one on each side of the 
glabella, in front of the compound eyes, are of the same nature (as 
Barrande assumes them to be), is an open question. That they are 
not the remains of antenne, as was supposed by Prof. M‘Coy, I think 
we may feel quite satisfied, as we know of no crustacean whatever 
with antenne arising from the dorsal aspect of the cephalic shield in 
the manner supposed by M‘Coy. . 
The antennz are either on the margin of the head as in many 
