27G PROCEEDINGS OF THE ACADEMY OF [1879. 



to separate subgenerically. They differ from all subcarboniferous 

 species of this group in having larger underbasals, fewer plates in 

 the interradial and anal areas ; in exhibiting a strong tendency to 

 a bilateral figure instead of a pentahedral; in having comparatively 

 much larger and higher first, and shorter second and third radials; 

 also in the exceedingly large first interradial and first anal plate. 

 Arms, so far as observed, free above the secondary radials, but 

 only toward the inner side of the ray; the outer side forming 

 almost a straight line. No pinnulse observed. Column round, 

 composed of alternately larger and smaller joints not tapering 

 in diameter downward. 



This division embraces the following species: 



*1878. Lithocrinus divaricatus Angelin. (Forbesiocr. divaricatus). Iconogr. 



Crinoid., p. 9, pi. 21, fig. 21, and pi. 28, fig. 3. Upper Silur. Gotland, 



Swed. 

 *1878 Lithocr. Milleri Angelin. (Forbesiocr. Milleri.) Iconogr. Crinoid, p. 9, 



pi. 21, fig. 16, and pi. 28, fig. 1. Upper Silur. Gotland, Swed. 

 *1878. Lithocrinus obesus Angelin. (Forbesiocr. obesus.) Iconogr. Crinoid., p. 



9, pi. 21, fig. 18, and pi. 28, fig. 2. Upper Silur. Gotland, Swed. 

 *1.878. Litbocr. robustus Angelin. (Forbesiocr. robustus.) Iconogr. Crinoid., 



p. 9, pi. 21, figs. 11, 12. Upper Silur. Gotland, Swed. 



9. ONYCHOCRINTJS Lyon & Casseday. 



1859. 0nyc7iocri?ius, L. & C. Am. Journ. Sci., vol. xxix. p. 77. 



1801. Onychocrinus, Meek & Worth. Geol. Rep. Illinois, vol. ii. p. 242. 



18G1. Forbesiocr inus, Hall. Bost. Journ. Nat. Hist., vol. vii. p. 321. 



Body extended in five free rays, which are sometimes spread 

 out horizontally; arms resembling the talons of a fowl. Calyx 

 depressed saucer or low cup-shaped. 



Underbasals three, of unequal size, rarely seen beyond the 

 column. Basals five, four with obtuse angles, the fifth with a 

 truncated or slightly excavated upper side. Radials four to five 

 (rarely six to seven) by five; comparatively large, almost of equal 

 size. At the third, fourth, or fifth plate, the rays become free, 

 after which they divide once, each division giving off the true 

 arms. Arms vei-y short, brandling once or twice, disposed in 

 clusters at the extremities, and in some species along their sides 

 also; composed of single joints with waving sutures and deep 

 ventral furrow. In the anal area there is a series of from three to 

 five very narrow, quadrangular plates, which rests upon the trun- 

 cated or slightly excavated upper side of the basal, and forms a 

 small lateral proboscis as in Taxocrinus. Interradials three to 



