I 



I 



1881.] NATURAL SCIENCES OF PHILADELPHIA. 325 



that at each side of the ray the larger plates alternate with the 

 smaller ones, and the former abut laterally against an arm open- 

 ing. The appendages are very heavy, composed of strong nodose 

 plates ; their cross-section, as that of their inner passage, oval, 

 higher than wide (PI. 18, fig. 5). At each side of the base of each 

 arm, there is a respiratory (?) pore ; that of one side is located at 

 some distance from the arm openings, the other and smaller one 

 lies close to it. The pores are so arranged that the larger ones 

 stand a,t one side of the appendages in front, at the other behind 

 the arm with which the}' are connected. Similar pores are placed 

 beside the proximal arms, but these pass directly through the 

 main body. Anal tube long, subcentral, composed of nodose 

 pieces. Column round, of moderate size ; central canal of medium 

 width, pentalobate. 



Geological Position^ etc. — Steganocrinus, so far as known, is 

 restricted to the age of the Burlington limestone, and has been 

 found onlj^ in America. 



We recognize the following species : — 



I860. Steganocrinus araneolus Meek and Worth. (Actinocr. araneolns) Proc. 



Acad. Xat. Soi. Phila., p. 387 ; Steganocr. araneolus, 186t;, (jeol. Rep. HI., 



ii, p. 198, PI. 15, fig?. 1 a, b. Lovrer Burlington limest. Burlington. Iowa. 

 *185d. Steganocr. conoinnus Shumard. (Actinocr. concinnus) Swallow's Geol. 



Rep. Missouri, pt. ii, p. 189, PI. A, fig. 5 ; Meek and Worth., 1866, Actinocr. 



concinnus, Geol. Rep. 111., p. 200, PI. 15, figs. 9 a, b. Upper Burl ngton 



limest. Burlington, Iowa. 

 Syn. Actinocr. validus Meek and Wortben, 1860, Proc. Acad. Xat Sci. Phila. 



p. 384. 

 1858. Steganocr. pentagonus Hall. Type of the genus. (Actinocr. pentagonusj 



Geol. Rep. Iowa, i, pt. ii, p. 577, PI. 10, figs. 6 a, b ; Meek and Wortheo, 



1866, Steganocr. pentagonus, Geol. Rep. 111., ii, p. 198; Ibid., 1868, iii, p. 



47-1, PI. 16, fig. 8. Lower Burlington limest. Burlington, Iowa. 

 1858. Steganocr. sculptus Hall. (Actinocr. sculptus— not Miller) Geol. Rep. Iowa, 



i, pt. ii, p. 582, PI. 10, figs. 11 a, b; Meek and Worthen, 1866, Steganocr. 



sculptus, Geol. Rep. 111., ii, p. 198. Lower Burlington limest. Burlington, 



Iowa. 



18. AMPHOEACRINUS Austin. 



1848. Austin. Quart. Jouru. Geol. Soc. London, iv, p. 292. 

 1873. Meek and Worthen. Geol. Rep. 111., v, p. 386. 



Not Roemer, 1855. Lethaea Geogn. (Ausg. 3), p. 250 = Agarico- 



erinus. 

 Not Hall, 1861. Bost. Journ. Nat. Hist., p. 561 = Agaricocrinus. 

 Not Meek and Worthen. Geol. Rep. 111., ii, p. 209 = Dorycrinus. 

 Syn. Amphora. Cumberland, 1826. Reliqu. Confeerv., p. 26. 

 Syn. Actinocrinus Phillips lin part), 1886. Geol. Yorkshire, p. 206. 

 Syn. Actinocrinus Hall (in part), 1860. Supp. Geol. Rep. Iowa. 



