590 CALIFORNIA ACADEMY OF SCIENCES. 



mm. The axis is broad, conical and prominent, occupy- 

 ing^ a little less than one-third the width of the tail on the 

 anterior margin. It is marked with eleven rings; these 

 become smaller and smaller and end in an obtuse point. 

 Each ring is distinctly ornamented along the center by a 

 series of nodes, arranged into three double rows of two 

 each. The sides of the axis are smooth. 



The lateral lobes are slightly flattened on top to the 

 fulcral point. They are marked with seven pleurae; the 

 grooves between the pleurae are deep and distinct, each 

 being rounded on top and ornamented with a single node 

 at the fulcral point; here they bend suddenly and join 

 the marginal border. 



Locality and position: Lower Coal Measures, T. v 

 N., R. xvi W., Sec. 17, near center of northwest quarter 

 of the section, Conway county, Arkansas. From the 

 collection of the Geological Survey of Arkansas, now at 

 Stanford University. 



Affinities and differences: This species in some of its 

 features resembles PJiillipsia Rtvineri Moller, Ueber die 

 Trilobiten Steinkohlen formation des Ural, pi. ii, fig. 17, 

 especially in the markings of the tail, which shows seven 

 pleurse ornamented by a single node at the fulcral joint, 

 but it differs in form and especially in the marking of the 

 axal lobe, so much so that it could not be placed under 

 MoUer's species. There is also a resemblance of this 

 species with Phillipsia ( Griffitliides) scitiila Meek & 

 Worthen, from the Illinois Coal Measures. It has the 

 same number of rings in the axis of the tail, and the same 

 characteristic pleune and ornamentation, but the Arkan- 

 sas species differs greatly in size and also in the number 

 of pleural, seven instead of six. The axis is not as wide 

 as in Griffithides scitula and not distinctly flattened on each 

 side. The limb, although moderately wide and smooth, 



