1881.] NATURAL SCIENCES OF PHILADELPHIA. 30T 



1878. (?)Perieohoor. radiatns Angel. Iconogr. Crin. Suec, p. 7, PI. 10, figs. 1 and 



2, and PI. 23, fig. 3; and PI. 27, figs. 6, 7. Upper Silur. Gothland, 



Sweden. 



This form differs in the size, in the style of ornamentation, and the greater 



number of secondary radials, from the typical species. 



1878. Periechocr. soanicus Angel. loonogr. Grin. Suec, p. 7, PI. 19, figs. 16, 16 a. 



Upper Silur. Gothland, Sweden. 

 *1878. Periechocr. Schultzianas Angel. (Actinoor. Schultzianus). Iconogr. Crin. 



Suec, p. 6, PI. 18, fig. 13. Upper Silur. Gothland, Sweden. 

 *1867. (?) Periechocr. semiradiatus Hall. (Saooocr. semiradiatus). 20th Rep. N. 

 Y. St. Cat. Nat. Hist., p. 37, PL 10, fig. 1. Niagara gr. Racine, Wis. 

 Desc. from natural casts. 

 *1862. Periechocr. speciosus Hall. (Saccocr. speciosus). Paleont. N. Y., ii, p. 

 205, PI. 44, figs. 1 and 2; also Roemer, 1860, Silur. Fauna West. Tenn., p. 

 42, PI. 3, fig. 4. Niagara gr. Western Tennessee. 

 *1861. Periechocr. tenuidiscus Hall, (Actinocr. (?) tennidiscus). Desc. New 



Spec. Pal. Crin., p. 14. Lower Burlington limest. Burlington, Iowa. 

 *1861. Periechocr. Whitei Hall. (Actinocr. — Megistocr. — Whitei). Desc. New 

 Spec Pal. Crin., p. 2 ; also Bost. Journ. Nat. Hist., p. 271 ; Meek and 

 Worthen, 1873, MegistOCr. Saococr. Whitei, Geol. Rep. 111., v, PL 6, fig. 1. 

 Lower Burlington limest. Burlington, Iowa. 

 The name of this species was printed originally Actinocr. Uegistocr. ollicn- 

 lus, but Hall changed it before publication in writing a« given above. 

 Among the Photogr. Plates subsequently published by Hall of some of his 

 new species (drawn by Whitfield and photographed by Haines), we find that 

 , through mistake fig. 6 on PL 4 has been referred to Megistocr. Whitei. 

 This is beyond doubt Hall's Actinocr. glans, an entirely different form, 

 which has a long slender anal tube and simple arms, the reverse of MegistOCr. 

 Whitei, which has an anal opening through the test and branching arms. 

 The original, formerly in the collection of Rev. Wm. H. Barris, and now in 

 the Museum of Comp. Zoology at Cambridge, was returned by Hall labeled 

 Actinocr. eryx, which is identical with Actinoor. glans. The type speci- 

 men of Megistocr. Whitei is in the Museum at Ann Arbor. 



13. ABAC0CEI5TJS Angeliu. 



1878. Angelin. Iconogr. Crin. Suec, p. 19. 



1879. Zittel. Handbuch der Palseontologie, i, p. 373. 



Syn. Actinocrinus Goldfuss (in part\ 1826, Petref. Genn., i, p. 

 194. 



Ahacocrinus has its closest affinities with Megistocrinus Owen 

 and Shum., from which it differs in the number of basals, and 

 perhaps (?) in the construction of the vault, which in the former 

 is not known. It differs from Periechocrinus in being composed 

 of heavier plates, and in the number of basals. 



Angelin places Ahacocrinus with Cor ymbocrinus into a. sepa,ra,te 

 famil3\ The two agree remarkably in the arm structure, and both 

 have four basals ; but the latter plates which in Ahacocrinus are 



