SUBCLASS I 



TRILOBITA 



717 



Fig. 1378. 



Alhertella helenae Walcott. Lower Cambrian 

 Powell County, Montana (after Walcott). 



Family 7. Ceratopygidae Raymond. 



Ojnsthoparia ivüh suh-equal cephalon and pygidium, long, nearly smooth glahella. 

 Pygidium with long spines at the sides. Caiuljrian and Ordovician. 



Geratopyge Corda. Glabella long, narrow, with basal lobes. Pygidium with long 

 spines springing from the pleural lobes at the second annulation. Basal Ordovician ; 

 Euro2)e and North America. 



Alhertella Walcott (Fig. 1378). Eyes long, glabella with 

 three pairs of furrows. Pleura of third segraent of thorax 

 extended into spines. Cambrian ; North America and Asia. 



Family 8. Ellipsoce- 

 phalidae Matthew. 



Ojjisthoparia with 

 narrow free cheeJcs, small 

 eyes, smooth, imfurroioed 

 glahella, twelve to sixteen 

 thoracic Segments, and small 

 pygidium. Cambrian. 



Ellipsocephal'us Zenker 

 (Fig. 1379). Dorsal fur- 

 rows of the cephalon deep, 

 cheeks are very narrow. 

 Cephalon with a narrow, 

 raised border. Cambrian ; 

 Europe and North 

 America. 



Agraulos Corda. 

 Glabella faintly outlined, 

 cephalon without concave 

 or rimmed border. Cam- 

 brian; Europe and 

 America. 



Strenuella Matthew. Similar to Agraulos, but with a narrow 

 cephalon. Lower Cambrian ; America. 



Fig. 1379. 



Ellipsoceplialus hoffi 

 Schloth. Cambrian 

 (Etage C) ; Ginetz, 

 Bohemia. 



Fig. 1380. 



Caphyra radians 

 Barr. Ordovician 

 (Etage D) ; Königshof, 

 Bohemia. i/i (after 

 Barrande). 



riin around the 



Family 9. Remopleuridae Corda. 



Opisthoparia with large, faintly furrowed glahella, ivhich has a tongue-like anterior 

 ptrojection. Eyes very large, extending nearly around the glahella. Thorax of eleven to 

 thirteen segments. Pygidium small. Ordovician. 



Remopleurides Portlock, Pygidium wider than long, with two pairs of short 

 spines. Ordovician ; Europe and America. 



Gaphijra Barrande (Fig. 1380). Pygidium long and flat. Genal spines and 

 pleura of thorax flattened. Ordovician ; Europe and North America. 



Family 10. Bathyuridae Walcott. 



Opisthoparia with cephalon and pygidium usually nearly eqiial in size. Glahella 

 long, cylindrical, reaching nearly to the anterior margin. Eyes large and dose to the 

 glahella. Tliorax of nine segments. Pygidium more or less strongly rihhed. Middle 

 Cambrian to Ordovician. 



