CYSTIDS AND BLAST0ID3. 137 



Metablastus bipyramidalis (Hall). 



Plate xviii, flg. 13. 

 Pentrejnites bipyramidalis Hall, 1858: Geol. Sur. Iowa, vol. I, p. 607, pi. 



XV, fig. 2. 

 Meiablastm bipyramidalis Ethridge & Carpenter, 1886 : Cat. Blastoidea, 



p. 143. 



Similar to M. wortheni, but with very much longer ambu- 

 lacra; and with the periphery about midway between the 

 extremities. 



Horizon and localities — Lower Carboniferous, Keokuk 

 limestone : Boonville (Cooper county). 



Metablastus wortheni (Hall). 



Plate xviii, flg. 12. 



Pentremites wortheni Hall, 1858: Geol. Iowa, vol. 1, p. 606, pi. xv, fig. 1. 

 Peniremites wortheni Meek & Worthen, 1873: Geol. Sur. Illinois, vol. V, 



p. 506, pi. xiv. fig. 11. 

 Pentremites varsoviensis Worthen, 1875: Geol. Sur. Illinois, vol. VI, p. 



521, pi. xxxi, figs. 8-9. 

 Metablastus ivortheni Ethridge & Carpenter, 1886 : Cat. Blastoidea, p. 143. 

 Metablastus varsoviensis Ethridge & Carpenter, 1886: Cat. Blastoidea, 



p. 143. 



Very closely related, and perhaps identical with M. Uneatus, 

 but apparently having longer ambulacra and heavier basal cup. 



Horizon and Localities. — Lower Carboniferous, Keokuk 

 limestone: Boonville (Cooper county ); Warsaw (Illinois). 



Schizoblastus ? roemeri Shumaed. 



Pentremites roemeri Shumard, 1885: Geol. Sur, Missouri, Ann. Kep., p. 



186, pi. B, figs. 2a-d. 

 Pentremites sampsoni Hambach, 1884: Trans. St. Louis Acad. Sci., vol. 



IV, p 551, pi. ii, figs. 2-2a. 

 Schizoblastus sampsoni Ethridge & Carpenter, 1886: Cat. Blastoidea, 



p. 142. 



Eesembling 8. sayi somewhat, but less than one-quarter 

 the size. 



Horizon and localities — Lower Carboniferous. Chouteau 

 limestone (Kinderhook) : Sedalia, Providence (Boone county). 

 G— 10 



