578 PALAEONTOLOGY OF ILLINOIS. 



ARCHIMEDES MEEKANUS Hall. 



Pl.LXIII,flg.4. 

 Archimedes meekana Hall, 1857. Proc. Amer. Ass. Ad. Sci. Vol. 10, p. 178. 



Axis slender, probably not exceeding seven cm. in length; sur- 

 face minutely granulose; volutions 4 to 5 in two cm., shaft 

 thin, faintly spiral, and spreading gradually into the flange, the 

 lower side of which is generally furrowed (7. e. showing the base 

 of the branches.) Fenestrated expansion of unknown width, 

 diverging from the axial line at an angle of 65. Branches 

 rounded on the reverse, wider and faintly carinate on the ob- 

 verse, the carina with closely crowded small spines. Zooecia in 

 two ranges, 25 or 26 in five mm., with very small elevated 

 apertures. Fenestrules subquadrate on reverse, slightly longer 

 than wide, about 20 in one cm. Dissepiments two-thirds as wide 

 as the branches and even with them. 

 Diam. of shaft of strongest ex. 1.0 mm.; No. of vol. in 2 cm., 4.9. 



" " smallest " 0.6 " 5.0. 



average " 1.1 " 4.3. 



another " 1.0 " 4.0. 



In its general appearance the axis of this species resembles 

 that of A. proutanus Ulr., but differs in being more loosely 

 wound. The zocecia are considerably smaller, and the fenes- 

 trules and branches more numerous in a given place. 



Position and locality: Chester group; not uncommon at Ches- 

 ter, 111. Eare at Sloan's Valley and Grayson Springs, Ky. 



ARCHIMEDES DISTANS Ulrich. 



PI. LXIII, fig. 9-9b. 



Axis very slender and delicate, probably not exceeding eight 

 cm. in length; volutions 3 to 3.5 in two cm.; shaft delicate, 

 sub-spiral, spreading gradually into the flange, the lower side 

 of which is, particularly in young examples, strongly furrowed 

 vertically. Perforated frond from 1 to 4 cm. wide, diverging 

 from the axial line at an angle of from 45 to 50 degrees. On 

 the reverse the branches are rounded, about 23 in one cm., the 

 fenestrules oblong quadrate, being about as wide as the branches 

 and one-half of the width longer than wide, with 19 or 20 in 



