Bkkdk.| Carboniferous Invertebrates, 49 



spines and plates. Without doubt, if wo had entire specimens 

 from both formations to compare, they would be found to be 

 different ; but until such differences are found it is best to leave 

 them in the same species. 



Archaeocidaris megastylus. Plate VIII, fig. 7. 



Archceocidaris megastylus Shumard, Trans. St. L. Acad. Sci., i, p. 

 225, (185S): Keves, Geol. Surv. Mo., iv, p. 189, pi. xv, ff. 2a, b, (1894); 

 Proc. Iowa Acad. Sci. n, p. 189, pi. xvm, ff. 2a, b, (189.")). 



Shumard's description : "The interambulacral plates of this 

 species in the collection are large, -hexagonal, wider than long, 

 and rather thick. The areolar surface is very broad, nearly 

 circular, slightly concave at its exterior portion and rising 

 gently to the base of the central boss. It is encircled by a 

 single series of small, secondary tubercles. The boss is broad, 

 smooth, and the central tubercle deeply perforated. The pri- 

 mary spines are long, robust, cylindrico-fusiform, and the 

 transverse section circular. The surface is very finely striated 

 longitudinally; and studded either rather distinct granules or- 

 minute short spines, arranged spirally or promiscuously. The 

 ring at the base is oblique to the axis, its border neatly crenu- 

 lated, and the diameter less than the greatest diameter of the 

 spine. The socket is deep, rather wide, and its margins smooth. 

 The neck is marked with a slightly raised ring, which is finely 

 striated longitudinally." 



Range and distribution : Upper Coal Measures ; Kansas City. 



This species often attains a length of three inches or more. 

 ( >ur specimens are but spines, and they are worn so that the 

 minute surface markings are all removed, but, from their size 

 and shape, there is little doubt of their identity. 



OLIGOPORUS. 



Meek and Worthen, Proc. Acad. Nat. Sci. Phil., p. 474, (I860). 



Oligopoms? minutus. Plate VII, fig. 3. ■ 



Oligoporusf minutus Beede, Kans. Univ. Quart., viii, p. 126, pi. xxxii, 



f. 3, (1899i. 



Small, depressed globular, melinitic ridges not very distinct. 

 There are four columns of pores, each column consisting of two 

 rows, in each ambulacral area : each row is generally, though 

 not always, made up of two pores placed side by side and very 



