1881.] NATURAL SCIENCES OF PHILADELPHIA. 309 



It lies directly above one of the basals, resting upon its truncate 

 upper side. Second series composed of three plates, the middle 

 one extending beyond the other two ; the two outer ones in line 

 with the second series of interradials (not the first as is usually 

 the case), and rests against the superior edges of the second (not 

 the first radials), these again are followed by five or six rows of 

 plates, generally of three each, which decrease in size upward. 

 The plates of the interaxillary areae are numerous. 



There is a single large plate in each of the two first series, which, 

 together with the upper interradial plates, connect the two main 

 arm-trunks with the body walls. Construction of the vault 

 unknown. 



Column large, composed of rather high, alternately thicker and 

 thinner joints. 



Geological Position, etc. — Abacocrinus, so far as known, is con- 

 fined to the Upper Silurian of Europe. 



Angelin places here the following species : 



1878. Abacocrinus Cappelleri Angelin. Iconogr. Crin. Suec, p. 19, PI. 3, figs. S, 8 a. 



Upper Silur. Gothland, Sweden. 

 1878. Abacocr. medius Angelin. Iconogr. Crin. Suec, p. 19, PI. 24, fig. 1. Upper 



Silur. Gothland, Sweden. 

 1878. Abacocr. tessellatus Angl. Iconogr. Crin. Suec, p. 19, PI. 18, fig. 6, and PI. 



23, figs. 24, 25. Upper Silur. Gothland, Swelen. 

 1826. Abacocr. tesseracontadactylus G'-ldf. (Aotinocrinus tesseracontadactylus), 



Petref. German, i, p. 194, PI. 59, fig. 5 ; Angelin, 1878, Ababocrinus, (type 



of the genus). Iconogr. Crin. Suec, p, 19, PI. 18, figs. 2, 5, and PI. 23, figs. 



23, 23 a. Upper Silur. Gothland, Sweden. 



14. MEGISTOCRINUS Owen and Shumard, 



1852. Ow. & Shum. U. S. Geol. Rep, Iowa. "Wis. & Minn,, p, 594. 



1857, Lyon, Proc. Acad, Nat. Set. Phila., p. 412, 



1858, Hall, Geol. Rep. Iowa, 1,, pt. 11, p. 479, 



1859, Lyon «fe Casseday. Amer, Jour of Scl,, vol, 28, p, 243. 

 1862, White. Proc. Bost. Soc. Nat, Hist., p. 16, 



1869. Meek & Worth. (In part), Proc. Acad, Nat. Scl. Phila., p, 163. 



1873. Meek & Worth, (In part). Geol. Rep, 111, v, p, 393, 



1876. White. Proc. Acad. Nat, Scl., Phila., p. 29. 



1878. Barris. Proc. Davenport. Acad. Nat. Scl., 11 , p. 285. 



1879. Zlttel. Handbuch der Palaeontologle, 1, p. 371 (not Hall, 1861, 



Bost. Journ. Nat. Hist., p. 271 ; nor Wlnchell and Marcy, 1866, 

 Mem. Bos. Soc. Nat. Hist., pp. 87 and 110 = Periechocrinus), 



Syn, Aetinocrinus Hall, 1858, Geol, Rep, Iowa, 1, pt, 11, pp, 571 and 

 573. 



Syn, Aetinocrinus Lyon, 1857. Geol. Rep. Ky., ill, p. 479. 



Syn. Sagenocrinus K.ngQ\\n, 1878 (in part). Iconogr. Crin. p, 8. 



