1896.] -"'^ [Smith. 



the axis is entirely different, so much so that it would not warrant its 

 reference to the Illinois species. 



"It is doubtful in our present state of knowledge whether PhilUpsia 

 ( Griffithides) scitula M. and W. should not be referred to the older name 

 of PhilUpsia cliftonensis Shumard, from the Upper Coal Measures, 

 Clifton Park, Kansas, described from a pygidium. Dr. Shumard says 

 that the axis has from thirteen to fourteen subgranulose rings and seven 

 side segments. A thorough study of all these allied sj^ecies may neces- 

 sitate their reference to the older name ; but for the present it would be 

 advisable to give the Arkansas species a new name on account of the 

 ornamentation of its tail." 



Class Arachnoidea. 

 Order XipJwsura. 



Genus undetermined. Prestwichia '? 



In the Lower Coal Measures of White county, Arkansas, 9 N., 4 W., 

 section 6, was found the mould of a part of the body of a crustacean 

 that seems to belong to the family of the Hemiaspidw, and yet differs 

 from all known genera of this family in being armed with two rows of 

 spines instead of only one. 



Too little of the body is known for a generic description. 



PROC. AMER. PHILOS. SOC. XXXY. 152. 2 I. PRINTED DEC. 17, 1896. 



