ARCHAEOCIDARIS. 271 



*Archaeocidaris mucronata Meek and Worthen. 

 Plate 14, figs. 3a, 3b, 4. 



Archaeoddaris mucranaius Meek and Worthen, 1800, p. 395; 1866, p. 295, Plate 23, figs. 3a-3c; Klein, 



1904, p. 52. 

 Archacocidaris ornatm White, 1877, p. 104, Plate 0, fig. 7a (non Echinocrinua [Archacocidarw] ornaliu 



Kiohwald, 1860, for which see p. 274; non Archaeociddfit ornntux Xrwborry, 18(11; non Archaeo- 



cidarix ornnta Lambert and Thii'ry, 1910, p. 124, for which see p. 267). 

 Archaeocidnris t/nicrotiata Keyes, 1895, p. 188; Lambert and Thii'ry, 1910, p. 124. 



Known only from dissociated plates and spines. Interambulacral plates hexagonal, 

 wider than high, width 0.5 of an inch, height 0.35 of an inch. Primary spines long, tapering, 

 slightly compressed, or nearly circular in section, and apparently a little curved near the base, 

 smooth proximally, beyond which they are armed with strong, sharp lateral spinulcs directed 

 obliquely distally. Length of a primary spine 2.6 inches, greatest diameter of shaft 0.16 of an 

 inch. 



Chester Group, Lower Carboniferous, Liberty, Randolph County, and Chester, Illinois. The 

 spine figured by Dr. White (1877) as ornatus is apparently referable to this species and is from 

 the Carboniferous (Coal Measures) of Ojo del Oso, near Fort Wingate, New Mexico; this speci- 

 men is in the United States National Museum Collection 8,472. 



*Archaeocidaris dininnii White. 

 Plate 14, figs. 5a-5b. 



Archaeocidarui dininnii White, 1880, p. 260, Plate 1, figs. 13-15; 1880a, p. 131, Plate 35, figs. 6a-6c; 



Keyes, 1894, p. 130, Plate 15, figs. 6a-6c; 1895, p. 190, Plate 18, figs. 6a-6c. 

 Archaeocidaris dininni Klem, 1904, p. 48; Lambert and Thiery, 1910, p. 125. 



Known only from primary spines which are fusiform, 50 to 60 mm. long, with a greatest 

 diameter of about 5 mm. Above the short plain neck the whole spine is studded with many 

 irregularly disposed spinules, 1 to 2 mm. long, which stand out nearly at right angles to the 

 shaft, except near its apex, where they are directed distally. The spinules are usually more 

 numerous and stronger upon the lower portion of the spines, and upon the middle portion of 

 some of them the spinules are obsolete. The smaller spines are usually more slender or less 

 fusiform than the larger. A striking feature of this species is that the spinules are directed at 

 right angles to the shaft. 



Upper Coal Measures, near Tecumseh, Nebraska, cotype in United States National 

 Museum Collection 8,031. Upper Coal Measures, Kansas City, Missouri; Red Oak, Iowa 

 (Klem). 



