l6o SMITHSONIAN INSTITUTION 



ANISOCRINUS Angelin 

 Plate X, figs, i-p 



Anisocrinus Angelin, Icon. Crin. Sueciae, 1878, p. 13. — Wachsmuth and Springer, Revision Palaeoc- 

 rinoidea, pt. 1, 1879, p. 37; ibid., pt. 3, 1886, p. 143. — Von Zittel, Handb. Palaeontologie, I, 1879, 

 p. 356; Grundziige Palaeontologie, 1895, p. 138. — Zittel-Eastman, Textbook Palaeontology, 1896, 

 p. 164 (2d Ed., 1913, p. 203). — Jaekel, Zeitschr. deutsch. geol. Ges., XLIX, 1897, p. 46 (separate). — 

 Bather, Rep. British Assoc, for 1898 [1899], p. 923; Treatise on Zoology (Lankester), pt. 3, 

 p. 189. — Springer, Amer. Geologist, XXX, 1902, p. 94; Jour. Geology, XIV, 1906, p. 479. 



Lecanocrinus Angelin (in part), Icon. Crin. Sueciae, 1878, p. 11. 



Fig. 15. Anisocrinus 



Lecanocrinidae with rays partly separated by solid plates arched over by 

 brachials. Crown usually ovoid, truncate above. Inf rabasals more or less erect, 

 taking part in the calyx wall. Radianal irregularly under right posterior radial, 

 resting on basals, and generally not touching right anterior radial; exception- 

 ally oblique, or wanting. Anal x alone, or followed by others. Interbrachials 

 usually one very large plate (exceptionally more than one smaller in succession) 

 filling the interradius, with rays interlocking above. Primibrachs two. Arms 

 usually dichotomous, interlocking, and infolding almost at a right angle. 

 Column not enlarging at the calyx. 



Genotype. Anisocrinus interradius Angelin. 



Distribution. Silurian; Sweden and the United States. 



Anisocrinus may be described as a combination of Lecanocrinus and Clidochirus, with 

 solid interbrachial structures added. Its most striking peculiarity in typical forms is the 

 relatively enormous first interbrachial plate, usually the only one, completely filling the inter- 

 radius and closely arched over by the abutting rays. 



The calyx plates are rather evenly curved, without marked depressions at the sutures or 

 in the interbrachial region, producing a generally unbroken surface. 



The radianal in this genus is in an intermediate position and somewhat inconstant, 

 usually retaining the angular lower face and general form of a radial, but sometimes not 

 touching the right anterior radial, and therefore not quite in primitive position ; exceptionally 



