CYSTIDS AND BLASTOIDS. 133 



Echinodiscus kaskaskiensis (Hall). 



I'latexviil, 11^. 3. 



Agelacrinus kaskaskiensis Hall, 1858: Geol. Iowa, vol. I, p. 696, pi. xxv, 



fig. 18. 

 Echinodiscus kaskaskiensis Miller, 1891 : JST. A. Geol. and Pal., p. 2-41. 



Discoid, with an apparently entire apex, from which the 

 rays proceed. Rays six, radiating and curving toward the 

 margin so as to come nearly in contact on the periphery ; com- 

 posed of uniform plates which are creuulate or poriferous at 

 their interlocking edges. Intermediate spaces occupied by 

 plates of hexagonal or irregular forms, nearly tlat. Surface 

 finely granulated. (Hall.) 



Horizon and localities. — Lower Carboniferous, Kaskaskia 

 limestone: Ste. Mary ( Ste. Genevieve county); Kaskaskia 

 ( Illinois ). 



Echinodiscus sampsoni Miller. 



Echinodiscus sampsoni Miller, 1891: Geol. Sur. Indiana, 17tli Ann. Rep., 

 p. 76, pi. xii, fig. 16. 



Almost too imperfect for recognition. From the fragments 

 known, it must have been considerably larger than -E7. Icaslcas- 

 Mensis. 



Horizon and localities — Lower Carboniferous, Keokuk 

 limestone: Boonville ( Cooper county). 



Pentreinrtes elongatus Shumard. 



Plate xviii, flg. 4. 



Pentremites elongatus Sliumard, 1855: Geol. Sur. Missouri, Ann. Rep., 



p. 187, pi. B,fig. 4. 

 Pentremites elongatus Shumard, 1858: Trans. St. Louis Acad. Sci., vol. I, 



p. 244. 

 Pentremites elongatus White, 1863: Boston Jour. Nat. Hist., vol. VII, p. 



488. 

 Pentremites elongatus Etheridge & Carpenter, 1886: Cat. Blastoidea, p. 



161, pi. i, figs. 4-5. 



• Calyx elliptical, elongated and attenuated upward, from 

 one and three-quarters to twice as long as wide ; summit con- 

 vex and more or less contracted ; base truncated but convex, 

 small, but wider than the summit ; section roundly pentagonal ; 

 periphery as nearly as possible equatorial. Basal plates small, 



