76 CARBONIFEROUS TRILOBITES. 



the researches into the " Challenger " collections now in progress^ will reveal 

 many others in this interesting group. In one instance, Sphceroma (PI. IX, fig. 

 9), the pore seems really to be on the line of the suture of the glabella, the free 

 cheeks of the Trilobite being represented in the Isopod by the first thoracic 

 somite which wraps around the sides of the head in a similar manner. 



In Serolis (PI. IX, fig. 8) the pore, which forms rather an elongated slit (p), 

 is in the centre of the margin of the first thoracic somite, at a distance from the 

 compound eye, and has no relation to any suture. These puncta may be, like the 

 fenestrce in the head of Blatta orientalis, either rudimentary ocelli or the seat of 

 some other nerve-sense, and may have been, as in Blatta and in Serolis, covered 

 with a thin transparent portion of the integument, which served either as a simple 

 eye, a tympanum, or an olfactory pore. We have referred to these fenestras in the 

 head of Blatta because they are placed, like those in the Trilobites, on a suture of 

 the head, and in front of the compound eyes. 



We hope to have some further information to offer on this subject upon a 

 future occasion, meantime other workers may be able to assist with suggestions 

 and specimens to elucidate this interesting point, for which we shall be only too 

 thankful. 



