ART. 21 ORDOVICIAN TRILOBITES ULRICH 9 



regarded as substantiating these claims are given in Plate 8. It 

 may be noted that even the anterior spines of Telephus are sug- 

 gested in Glaphurus^ and that we are again reminded of that genus 

 by the spines on the rim of the free cheeks. 



Raymond places GJaphwms in the Odontopleuridae (Acidaspidae), 

 but in my opinion this genus, and particularly Raymond's Glaph- 

 urina decipiens^ which belongs to the group of species for which I 

 am proposing the new genus Glaphurina^ is closer to Telephus and 

 possibly also to Cyheloides than to any of the true Odontopleuridae. 

 In estimating the family relations of these genera I am inclined 

 to place as much or more weight on their pygidial characters than 

 on those of the cephalon. The pygidia of the first two indicate 

 close relationship, but those of the encrinurid genus Cyhelopsis and 

 those of the Odontopleuridae suggest very distinct families, both 

 of which are quite apart from the Telephidae. Doubtless many 

 kinds of trilobites with intermediate structures existed, and some 

 of these must be discovered before anything like a clear conception 

 of the genetic relations of the Remopleuridae, Telephidae, Encri- 

 nuridae, and Odontopleuridae may be acquired. 



The descriptions of the species of Telephus are followed by briefer 

 statements concerning the genotype and hitherto only known and 

 unquestionable species of Glaphurus^ a new species of the same 

 genus from the southern Appalachian region, and the four species 

 that are now known of the proposed genus Glaphurina. Though 

 perhaps inadequately described this can not be said of the illus- 

 trations. These are ample and true to nature, which after all are 

 the most desirable qualities of a paleontological contribution. 



NEED OF DISCRIMINATING SPECIES CLOSELY 



That some may question the wisdom of dividing the " species " 

 as closely as it is done in following pages is suggested by the 

 rektive looseness of conception indicated by specific identifications 

 of species of Telephus in European publications. If complete 

 specimens were always available the multiplicity of characters that 

 go to make up each particular specific combination would render 

 its discrimination and subsequent recognition much easier and more 

 certain than with only cranidia on which to base conclusions. 

 After all, it is not to be expected that striking differences should 

 occur in the cranidia of closely allied species because conspicuous 

 modifications of its characters commonly are of higher taxonomic 

 significance. Striking modifications that are of more strictly specific 

 importance, such, for instance, as in surface markings, do occur 

 in the cranidium, but as a rule most of them pertain to the free 

 cheeks, the thoracic segments, and the pygidium. In the free cheeks 



