TRILOBITA— PROP ARIA. 327 



183. D. micrurus (Green). Devonic. 



Pygidium very similar in form and surface markings to that 

 of D. pleuroptyx but its axis has 20 or 21 annulations and there 

 are 14 to 16 pleura; these latter are likewise less curved than in 

 D. pleuroptyx. 



Helderbergian of New York, etc. 



Fig. 1642. D.ilmaniles nasulus, cephalon and pygidium. ■ (After Hall.) 



184. D. pleuroptyx (Green). (Fig. 1643.) Devonic. 



Marginal rim anterior to glabella crenulate. Pygidium with axis 

 of about 17 annulations; pleura (11-13) marked by a medial 

 groove. Surface of entire test granulose. 



