70 Field Museum of Natural History — Geology, Vol. IV. 



Thorax known only by a few detached segments which indicate that 

 it was narrow and elevated. 



Pygidium subtriangular, terminating in a rounded obtuse angle, 

 strongly elevated and trilobed. Axis convex, marked by six or seven 

 annulations; it tapers gradually and is truncated posteriorly so that the 

 dorsal furrows instead of meeting at a point posteriorly are joined by a 

 short transverse furrow; the pleural lobes slope abruptly from the dorsal 

 furrows to the margins; each lobe consists of five segments, faintly 

 grooved on their distal portion; the segments merge into a smooth, 

 undefined, marginal border. 



The type specimen is a perfect cranidium with the following dimen- 

 sions: Length on median line 7.8 mm.; length including genal angles 

 9.0 mm.; width 14.0 mm.; length of glabella including occipital ring 5.4 

 mm.; length of glabella without occipital ring 4.5 mm.; width of gla- 

 bella at anterior lobe 3.5 mm.; width of glabella at posterior lobes 5.4 

 mm. A detached pygidium gives the following measurements : Length 

 3.4 mm.; width 6.4 mm.; thickness 4.8 mm. 



Remarks. — This species was considered by Savage to be identical 

 with Calymene fayettensis of the lower beds, but it is distinguished from 

 that species by its surface ornamentation, its shorter glabella, its larger 

 anterior margin, its longer and more prominent palpebral lobes, the 

 transverse furrow connecting the dorsal furrows on the pygidium and 

 its smaller size. In surface ornamentation this species resembles C. 

 senaria but is distinguished from it by its longer palpebral lobes, its 

 relatively short and more elevated glabella. It is distinguished from 

 all species known to the writer by the nodes, which are situated in the 

 dorsal furrows on each side of the anterior lobe of the glabella. C. 

 mammillata bears two nodes, but they are situated on the anterior 

 margin. 



Locality and horizon. — Limestone layers of the Upper Maquoketa 

 beds at Patterson's Springs near Brainard, Iowa. No complete speci- 

 mens have been observed by the writer, but cranidia, free cheeks, 

 thoracic segments and pygidia are comparatively abundant. 



Family CHEIRURID^, Salter. 

 Genus CERAURUS Green 1832. 



"Entire body subovate in outline. Cephalon subsemicircular or 

 subsemielliptical in outline, genal angles produced into spines; gla- 

 bella strongly convex, broadest in front, with three pairs of deep lateral 

 furrows; posterior limbs of the facial sutures cutting the lateral margins 



