268 THE CHICAGO ACADEMY OF SCIENCES. 



Remarks. This species, next to Calymene niagarensis , 

 probably has the widest distribution of any of the trilobites of the 

 Niagaran fauna of the Chicago area. The glabella is the por- 

 tion of the species most commonly preserved, and the specimens 

 are usually larger than the dimensions given above, a width of 

 18 mm. being a not unusual size. Specimens with the cheeks 

 well preserved, and especially with the free cheeks are rarely 

 met with. No specimen with the thorax and pygidium pre- 

 served has been observed from the Chicago area, but a specimen 

 in that condition from Madison, Indiana, is preserved in the 

 collections of the Walker Museum. Isolated pygidia are 

 sometimes met with, but not often. 



The species is somewhat closely allied to the European 

 5. mirus Beyrich, but the body of the European species is broader 

 throughout, the head of the American species is much more 

 globular in form with the glabella much more protuberant 

 beyond the frontal margin. The pygidium also of the American 

 species has the pleural lobes much more reduced in size and 

 with the free points of the pleural segments more produced'. 



Localities. Bridgeport, Lemont, Romeo, Joliet, etc. 



Genus 1 8. DEIPHON Barrande. 



Cheeks of the head reduced to elongate, recurved, spine- 

 like processes; glabella sub-globular, comprised largely of the 

 frontal lobe which is greatly produced anteriorly, the lateral 

 furrows nearly or quite obsolete; free cheeks minute, eyes small, 

 occupying the angle between the spine-like fixed cheeks and the 

 glabella. Thorax with nine segments with free spiniform 

 pleura. Pygidium short, with two pairs of lateral, curved, 

 spiniform processes. 

 Deiphon americanus, n. sp., pi. xxiv, fig. 14. 



Description. Glabella produced anteriorly, the nearly 

 globular frontal lobe being larger than all the remaining portion 

 of the cephalon and being extended in its entirety beyond the 

 frontal margin. Back of the frontal lobe is a broad, rounded, 

 occipital furrow marked at either extremity in the casts, by a 

 conspicuous, circular, pit-like depression, these pits probably 

 representing a nearly obsolete pair of lateral furrows; occipital 

 segment narrow, arched transversely. Cheeks reduced to mere 

 spine-like processes which extend obliquely outward and back- 

 ward with a slight convex curve, their bases opposite the pit- 

 like depressions at the extremities . of the occipital furrow. 



