326 



NORTH AMERICAN INDEX FOSSILS. 



one half of the entire glabella; the anterior and second lateral lobes 

 somewhat confluent along their outer edges; the third not at all 

 confluent. Eyes elevated above the level of the glabella. Pygid- 

 ium subtriangular, pointed posteriorly; axis of ii annulations and 

 side lobes with about nine grooved pleura. Length of cephalon 

 to base of anterior spine 17.5 mm., width 33 mm. ; length of 

 pygidium 17 mm., width 20 mm.; length of axis 13 mm. 

 Niagaran of Indiana, Illinois, Arkansas and Wisconsin. 



Fig. 1640. Dahnanites achates. 

 (After Clarke.) 



Fig. 1 641. Dalmanites limulurtis. (After 

 Hall.) 



181. D. (Corycephalus) dentatus Barrett. Devonic. 

 Very similar in form to D. Hmulurus but lateral and front mar- 

 gins of cephalon with a row of prominent, short, triangular spines. 

 Thoracic pleura extended into sharp, posteriorly pointing spines; 

 pygidial pleura eight instead of eleven. Glabella and pygidium 

 coarsely papillose. 



Helderbergian of New York and New Jersey. 



182. D. nasutus (Conrad). (Fig. 1642.) Devonic. 

 Cephalon extended into a bifurcating spine. Pygidium pro- 

 longed into a single long spine. Entire surface of test pustulose. 



Helderbergian of New York, etc. 



