NO. 5 UPPER CAMBRIAN TRILOBITES RESSER 3 



On the other hand the subgenus Parairvingella, based on Chario- 

 cephalus {?) tumifrofis Walcott (not Hall and Whitfield) deserves 

 generic rank. Kobayashi's other subgenus Irvingellina based on Hall 

 and Whitfield's species falls in Irvingella, as subsequently discussed. 



It is doubtful whether Irving elloides, which is based on a single 

 incomplete cranidium, belongs in the family. The new genus, Dnini- 

 aspis, is added to the family Komaspidae. 



The family Komaspidae is characterized by a large, more or less 

 quadrate glabella which extends almost the full length of the 

 cranidium. Occipital furrow is deep and wide, and three pairs of 

 glabellar furrows are usually developed. The real pair, generally 

 deep, may or may not be interrupted in the center, and the next pair, 

 if visible, consists of short lateral indentations while the anterior pair 

 is always faint and situated far forward. Fixigenes essentially con- 

 fined to palpebral lobes. Brim narrow, usually simple, but may have 

 a narrow rim. Eyes large, in some species longer than the glabella. 

 Libragenes usually rather narrow. Pygidium has a wide well-seg- 

 mented axis ; pleural lobes fused, pleural furrows deep. Border 

 flattened or concave. 



I recently discussed the relation of Charioccphalus and Irvingella, 

 but now that many more species are determined, further remarks 

 will be in order. As the matter now stands this family contains the 

 following genera. 



Komaspis Kobayashi, 1935 



Glabella subconical ; brim concave with slight rim ; eyes moderate 

 in length ; anterior fixigenes developed. 

 j\Iiddle Cambrian, Asia. 



Charioccphalus Hall, 1863 



Glabella quadrate or expanded slightly forward ; brim a simple bar ; 

 eyes moderately to extremely long ; libragenes large ; anterior fixigenes 

 reduced or absent. 



Upper Cambrian (upper Franconia zones). North America. 



Irvingella Ulrich and Resser, 1924 



Glabella quadrate to subconical ; eyes always large ; anterior fixi- 

 genes present ; brim simple or slightly rimmed ; libragenes very 

 narrow ; pygidium like Chariocephalus. 



Upper Cambrian (lower and middle Franconia zones), North 

 America. 



