SUBCLASS I 



TRILOBITA 



17 



Family 7. Ceratopygidae Raymond. 



Opisthoparia with sub-equal cephalon and pygidium, long, nearly amooth glabella. 

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



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

 splines sjiringing from the pleural lobes at the second annulation. Basal Ordovician ; 

 Europe and North America. 



Habella with 



Pig. 137'. ». 



FAlipsocephalun h.offi 

 Scliloth. Cambrian 

 (Etage C) ; Ginetz, 

 Boliemia. 



Albertella Walcott (Fig. 1378). Eyes long, 

 three pairs of furrows. Pleura of third segment of thorax 

 ■ extended into spines. Cambrian ; North America and Asia. 



Family 8. Ellipsoce- 

 phalidae Matthew. 



Opisthoparia with 

 narrow free cheeks, small 

 eyes, smooth, unfurrov)ed 

 glabella, twelve to sixteen 

 thoracic segments, and small 

 pygidiuvi. Cambrian. 



Ellipsocephalus 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. 



Stremiella Matthew, 

 cephalon. Lower Cambrian ; America. 



Family 9. Remopleuridae Corda. 



Opisthoparia with large, faintly furrowed glabella, which has a tongue-like anterior 

 projection. Eyes very large, extending nearly around the glabella. Thorax of eleven to 

 thirteen segments. Pygidium small. Ordovician. 



Bemopleurides Portlock. Pygidium wider than long, with two j^airs of short 

 spines. Ordovician ; Europe and America. 



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

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



Fig. 137S. 



Alhertdla hdcnae Walcott. Lower Cambrian : 

 Powell County, Montana (after Walcott). 



Fig. 1380. 



CapTiyra radians 

 Barr. Ordovician 

 ( Etage D) ; Konigsliof, 

 Boliemia. Vi (after 

 Barrande). 



Similar to Agraulos, but with a narrow rim around the 



Family 10. Bathyuridae Walcott. 



Opisthoparia with cephalon and pygidium usually nearly equal in size. Glabella 

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

 glabella. TJiorax of nine segments. Pygidium more or less strongly ribbed. Middle 

 Cambrian to Ordovician. 



