710 



ARTHEOPODA 



PHYLUM VII 



Family 1. Agnostidae M'Coy. 



Hypo2Jaria with head and abdomen shields similar; free cheeks not visible from the 

 dorsal side. Thorax xvith two segments. Cambrian and Ordovician. 



Subfamily A. Condylopyginae Raymond. 



Agnostidae with many-lobed shields, long glabella ivhich expands totvard the front, 

 and long and broad axial lobe on pygidium.. 



Condylopyge Corda. Anterior lobe of glabella broad. Pygidium 

 with three pairs of middle - lobes, and a broad end -lobe. Middle 

 Cambrian ; Europe and North America. 



Pleuroctenium Corda (Fig. 1358). Similar to Condylopyge, but 

 with anterior lobe of glabella flattened, and crossed by radiating 

 grooves. Cambrian ; Europe. 



Diplagnostus Jaekel. Anterior middle-lobe divided. Axial lobe 

 of pygidium pointed behind. Cambrian ; Europe. 



Peronopsis Corda. Anterior middle lobe of glabella simple, not 

 wider than the part behind. Accessory lobes present at base of 

 glabella. Middle Cambrian ; Europe and North America. 



Subfamily B. Arthrorachinae Raymond. 



Agnostidae with middle lobe of glabella short and simple; small accessory lobes 

 present at base of glabella. 



Arthrorachis Corda. Ordovician ; Europe and North America. 

 Hypagnostus Jaekel. Axial lobe of pygidium narrow, pointed behind. 



Subfamily C. Agnostinae Jaekel. 



Agnostidae toith both shields sculptured. Middle lobe of cephalon long, narrowed 

 toward the front. Accessory lobes always present. 



Agnostus Brongniart (Figs. 1357, A ; 1359). Surface 

 smooth ; accessory lobes simple. Cambrian ; Europe and 

 North America. 



Ptychagnostus Jaekel. Surface wrinkled or otherwise 

 ornamented. Accessory lobes double. Cambrian ; Europe 

 and North America. 



Subfamily D. Phalacrominae Corda. 



Fig. 135S. 



Pleuroctenium 

 rjranulatum (Barr.). 

 Cambrian ; Skrey, 

 Bohfiinia. 5/j (after 

 Barrande). 



Fig. ]:;5'.i. 



Agnostus pisiformis (Linn.). 

 Cambrian ; Andiarnm, Sweden. 

 Complete individnal, and frag- 

 ment of limestone witli detaelied 

 cephala and pygidia. 



Agnostidae with shields scarcely lobed. 



Lejopyge Corda. Middle lobe of cephalon and pygidium Ijarely indicated- 

 Ordovician ; Europe. 



Phalacroma Corda. Cephalon and pygidium without lobes. Cambrian and 

 Ordovician ; Europe and North America. 



Family 2. Eodiscidae Raymond. 



Hypoparia of small size ; free cheeks not visible from the dorsal side ; thorax of three 

 segments ; pygidium annulated. Cambrian. 



