III. NOTES ON ORDOVICIAN TRILOBITES. II. 



ASAPHIDiE FROM THE BeEKMANTOWN. 



By Percy E. Raymond. 



Asaphids first become prominent in American faunas in the Beekman- 

 town, but few species ha\e been described from that formation, it being 

 the usual custom to refer any smooth-tailed species to Asaphns canalis. 

 A closer study of some of the material shows that the hypostoma of two 

 of the Beekmantown Asaphids is not forked, so that they can not belong 

 to the same genus as Asaphus canalis Whitfield, nor even to the same 

 section of the family. As for the Asaphus canalis of Whitfield, the writer 

 will attempt to show that it is more nearly related to Isoteliis than to 

 Asaphus, but that it can not be placed in either genus. 



Family ASAPHIDS Emmrich. 

 IsoTELOiDES Genus nov. 



This genus is proposed to include Asaphidce with forked hypostoma, 

 long and narrow form, narrow axial lobe, feebly outlined glabella which 

 does not reach front of cephalon, glabellar furrows faint or absent, neck 

 furrow nearly obsolete, and a small median tubercle present on the 

 glabella. Pygidium with prominent, narrow axial lobe, but with slight 

 traces of segmentation Flattened border present on pygidium and front 

 of cephalon. Type, Asaphus canalis Whitfield. 



This genus is separated from Asaphus because the glabella does not 

 reach to the front of the cephalon, nor does it expand toward the front, 

 because of the almost obsolete neck and dorsal furrows, the long and 

 narrow form, and the presence of a flattened border on cephalon and pygi- 

 dium. It agrees with Asaphus in the form of the hypostoma, which has 

 the wings separated from the convex body by deep grooves. It also 

 agrees with Asaphus in possessing a narrow axial lobe, a defined glabella, 

 and a median pustule on the posterior portion of the glabella. These are, 

 however, characters common to several genera among the Asaphidce. 

 The most important characteristics of the typical Asaphus seem to be the 

 short and wide form of the cephalon and pygidium, the absence of a 

 depressed border at either extremity, the fact that the glabella expands 



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