NO. 4 CAMBRIAN TRILOBITES, 2D CONTRIBUTION RESSER 13 



tion. Even though all bibliographic references are at hand, which 

 offers an advantage previous students of the group did not have, never- 

 theless the usual difficulties of working without specimens — with only 

 descriptions and drawings — renders some of the following decisions 

 of doubtful value. 



Each described genus is discussed and its validity judged as far as 

 the information available permits. Previous workers often considered 

 chiefly local material, and sometimes the rules of nomenclature were 

 not kept in mind. Therefore, it is hoped that the following discussion 

 will shorten the labors of the person who will monograph this interest- 

 ing group of trilobites. 



Diagnosis. — Eyeless trilobites of ordinary size. Glabella well de- 

 fined, tapered, with short recurved pairs of furrows. Genal spines 

 usually lacking. Surface granulated or lined, or both. Equivalent of 

 eye lines usually present. Thorax with about 15 segments; pleura 

 blunt. Pygidium small, well fused, with well-impressed dorsal fur- 

 row and pleural grooves. 



The family is evidently confined to the Middle Cambrian of the 

 Atlantic Province, with three Asiatic incursions. 



Synonyms of the various species are listed under the genera to 

 which they were last referred by competent students, but a list of 

 the genera regarded as valid follows. All species which appear refer- 

 able to the family, with two exceptions, can be cared for by using 

 existing genera. 



Conocoryphe Corda, 1847 Holocephalina Sailer, i8()4 



Ctenocephalus Corda, 1847 Da some to pus, new genus 



Bailiclla Matthew, 1885 HartshUUa Illing, 1915 

 Bmliaspis, new genus 



LiocepMlus Gronwall is evidently a synonym of Holocephalina, 

 and Hartella is eliminated as a synonym of Ctenocephalus. 



CONOCORYPHE Corda, 1847 



Conocoryphe Corda, Abli. k. bomischen Gesell. Wiss., vol. 5, p. 139, 1847. 

 Conocoryphe Mattheaw Trans. Roy. Soc. Canada, vol. 2, sec. 4, p. 103, 1885. 

 Conocoryphe Gronwall, Danmarks Geol. Unders., vol. 2, no. 13, pp. 82, 84, 

 213, 1902. 



The foregoing bibliography includes only those references which 

 contribute to the understanding of this and related genera. Species be- 

 longing to many other families have been referred to Conocoryphe, as 

 well as those representing other genera within the family. 



Diagnosis. — Eyeless trilobite, oval in outline. Glabella tapered, with 

 several sets of short, recurved furrows ; extends nearly to the anterior 



