200 PROCEEDINGS OP THE ACADEMY OF [1819. 



3. ANISOCRINUS Angelin 

 1878. Iconogr. Crinoid., p. 13. 



General form of body, including arms, ellipsoid. Calyx bowl- 

 shaped ; figure bilateral. 



Underbasals three, hidden by the column. Basals of medium 

 size, dissimilar in form. Primary radials three to five, the first 

 widest, almost as large as second and third together; the second 

 smallest of all. Secondarjr radials two, gradually increasing in 

 size upward, the bifurcating plate almost as wide as the third 

 primary radial. Arms apparently free above the secondai-y radials, 

 accumbent as in Ichthyocrinus, and composed of transverse joints. 

 Interradials one (sometimes with a small triangular piece above), 

 very large, resting with the lower angle against the short upper 

 lateral sides of the first radials, forming with them a compact wall. 

 Anals two, very large, the upper one the largest plate in the body ; 

 the acute angle of the lower leaning against the basals, with the 

 lower lateral sides i-esting against the adjoining s u brad ials, and its 

 upper lateral sides against the large first radials. The second 

 anal plate rests upon the upper truncated side of the lower one, 

 being in line with the interradial plates, and reaches like them up 

 to the top of the secondaiy radials. 



The arrangement and size of the interradial and anal plates are 

 the characteristic features of this genus. Angelin's descriptions 

 are rather indistinct on this point, and in order to have it properly 

 understood, we give almost a specific description, which will prob- 

 ably have to be modified when more species are discovered. 



Only two species are known. 



1878. Anisocrinus interradiatus Angelin. Type for the genus. Iconogr. Crin., 



p. 13, pi. 22, figs. 18, 18 a. Upper Silur. Gotland. 

 *1852. Anisocrinus Angelini Wachs. & Spr. (Lecanoerinus macopetalus Angelin 



(not Hnll). Iconogr. Crin., p. 12, pi. 19, figs. 3, 4; and pi. 22, fig. 24. 



Upper Silur. Gotland, Swed. 



The Swedish form with its enormous interradial plate is not 

 onty specifically but even generically distinct from Lecanocr. 

 macropetalus, Hall. Of the two specimens figured by Angelin, 

 the one, pi. 19, fig. 3, agrees in every respect with Anisocrinus, 

 while the other, fig. 4, differs from it in having a small, evidently 

 abnormal plate, intercalated on the posterior side. We propose 

 for this species the name of Anisocrinus Angelini, in honor of the 

 late- Prof. Angelin, the author of the genus. 



