SUMMARY. 149 



Family Marrellidje Walcott. 



Cephalon with long genal and nuchal spines. Eyes marginal. A single species : Marrella 

 splendcns Walcott, Middle Cambrian, British Columbia. 



Order Aglaspina Walcott. 



Body trilobite-like, with few thoracic segments, and a spine-like telson. Appendages bira- 

 mous. 



Family Aglaspidse Clarke. 



Cephalon trilobate, with or without compound eyes, seven or eight segments in the thorax. 



Genus Aglaspis Hall. 

 Compound eyes present, seven segments in thorax. Upper Cambrian, Wisconsin. 



Genus Molaria Walcott. 

 Compound eyes absent, eight segments in thorax. Middle Cambrian, British Columbia. 



Genus Habelia Walcott. 

 Compound eyes absent. Not yet fully described. Middle Cambrian, British Columbia. 



Subclass Xenopoda nov. 



Crustacea with more or less eurypterid-like form, one pair of uniramous antennae, biramous 

 appendages on anterior part of trunk, modified endopodites on cephalon. 



Order Limulava Walcott. 



Cephalon with lateral or marginal eyes and large epistoma. Body with eleven free seg- 

 ments and a telson. Cephalic appendages grouped about the mouth. 



Family Sidneyidae Walcott. 



Trunk probably with exopodites only, and without appendages on the last two segments. 



Telson with a pair of lateral swimmerets. 







Genus Sidneyia Walcott. 



Third cephalic appendage a large compound claw. Gnathobases forming strong jaws. Mid- 

 dle Cambrian, British Columbia. 



Genus Amiclla Walcott. 

 Middle Cambrian, British Columbia. 



Family Emeraldellidae nov. 



Trunk with biramous appendages in anterior part, and appendages on all segments except 

 possibly the spine-like telson. 



Genus Emcraldella Walcott. 



Cephalic appendages simple spiniferous endopodites. Fyes unknown. Middle Cambrian, 

 British Columbia. 



