354 PROCEEDINGS OF THE ACADEMY OF [1879. 



Geological position, etc. The genus is known only from the 

 uppermost part of the Subcarboniferous and from the Coal meas- 

 ures, and occurs both in Europe and America. 



We recognize the following species: 



*1S70. Hydreionocrinus acanthophorus Meek and Worthen. (Zeacr. Hydreion- 



ocr. acanthophorus.) Proc. Aend. Nat. Sci. Phil., p. 28; Geol. Surv. 111., 



vol. v. p. 563, pi. 24, fig. 11. Upper Coal Measures. Illinois and Iowa. 

 *1870. Hydreionocr. armiger Meek and Worthen. (Zeacr. (?) armiger.) Proc. 



Acad. Nat. Sci. Phil., p. 27 ; Geol. Rep. III., p. 547, pi. 21, fig. 3. Chester 



limest. Subcarb. Pope Co., 111. 

 *1850. Hydreionocr. depressus Troost. (Zeacr. depressus.) Cat. Pal. Foss. 



Tenn. ; Hall, 1858, Geol. Rep. Iowa, vol. i. pt. ii. p. 546. Chester limest. 



Subcarb. Kentucky and Alabama. 

 *1860. Hydreionocr. discus Meek and Worthen. (Zeacr. discus.) Proc. Acad. 



Nat. Sci. Phil., p. 390 ; Geol. Rep. 111., vol. II. p. 312, pi. 26, figs. 3 a, b. 



Upper Coal Measures. Illinois. 



(Compare with Hydreionocr. acanthophorus.) 



*1859. Hydreionocr. mucrospinus McChesney. (Zeacr. mucrospinus.) Desc. 



New Pal. Foss. p. 10 ; Trans. Chic. Acad. Sci., 1867, vol. i. p. 7, pi. 4, fig. 7. 



Coal Measures. Illinois. 

 1853. Hydreionocr. woodianus De Koninck. Type of the genus. Bull. Acad. Royale 



Belgique, pt. ii. p. 17, pi. 2, figs. 5, 5 a. Subcarboniferous. Richmond, 



Yorkshire, England. 



Doubtful Species, placed under the genus by De Koninck. Bull. Acad. 

 Royale, Belg., vol. iii. pt. ii. p. 13. 



1853. (?) Hydreionocr. calyx De Koninck and Lehon. (Zeacr. calyx.) Recherch. 

 Crin. Carb. Belg., p. 90, pi. 1, fig. 6 a-d. Lower Carboniferous. England 

 and Belgium. 



1836. (?) Hydreionocr. granulosus Phillips. (Poteriocr. granulosus.) Geol. 

 Yorksh., p. 205, pi. 4, fig. 2; Austin, 1843, Mon. Rec. and Foss. Crin., p. 

 77, pi. 9, figs. 3 a-f. Subcarboniferous. Bolland, England. 



1853. (?) Hydreionocr. McCoyanus De Koninck and Lehon. (Poteriocr. McCoy- 

 anus.) Rech. Crin. Carb. Belg., p. 91, pi. 1, fig. 7. Lower Carboniferous. 

 Vi.e, Belgium. 



1853. (?) Hydreionocr. Phillipsianus De Koninck and Lehon. (Poteriocr. Phil- 

 lipsianus.) Rech. Crin. Terr. Carb. Belg., p. 91, pi. 1, fig. 7. Lower Car- 

 boniferous. Vise, Belgium. 



1858. (?) Hydreionocr. scoticus De Koninck. Bull. Acad. Royale Belg., vol. iii. pt. 

 ii. p. 19, pi. 2, figs. 6, 7. Carboniferous. Glasgow, Scotland. 



B. Subgenus CCELIOCRINUS White. 



18G1. Poteriocrinus Hall (in part;. Bost. Jour. Nat. Hist., p. 300. 

 1863. Ccdiocrinus White. Bost. Jour. Nat. Hist., p. 497. 

 18G9. Cceliocrinus, subgenus of Poteriocrinus, Meek and Worthen. Proc. 

 Acad. Nat. Sci. Phila., p. 138. 



