PAL/EOCRINOIDEA. 



437 



become united to form an almost solid disc, which is slightly hollowed 

 above, and exhibits a group of pits, which probably lodged extensions of 

 the " chambered organ." The Silurian genus Edriocrinus was also free 

 in its adult condition, but underbasals are wanting, and it possesses other 

 peculiarities as well. 



Family 19. Catillocrinidce. — In this small family, the calyx is of 

 small size and of the " monocyclic " type. The radials are remark- 

 ably unequal in point of size, two of them being greatly developed, 

 and forming the larger part of the margin of the calyx. These carry 

 a much larger number of the arms than the three small radials. 

 The arms are simple, uniserial, and long, and the column is round. 



Fig. 310. — Side-view of a complete 

 example of Agassizocrimis dactyli- 

 for)iiis (^ — Astylocrimis leevis, F. 

 Roemer). Carboniferous, North Am- 

 erica. (After Meek and Worthen.) 



Fig. 311. — Dissected calyx of Agassizocrimis. b, 

 Underbasals ; /, Basals ; r, Radials ; a, Anal plates. 

 (After Hall.) 



The type-genus is Catillocrimis, the geological horizon of which is 

 the Carboniferous rocks of North America. 



Family 20. Calceocrinidcz (= Cheirocrinidce). — This family includes 

 only the aberrant genus Calceocrinus ( — Cheirocrinus), which ranges 

 from the Ordovician to the Carboniferous. In this genus the small 

 and irregular calyx, with its crown of arms, is fixed in such a way as 

 to hang downwards from the summit of the column. The calyx is 

 " monocyclic," and there are only three basals, which, in the natural 

 position of the cup, are situated posteriorly. The radials are of un- 

 equal size, only three of them bearing arms. The basals and radials 

 are united by ligaments and muscles, so that a distinct articulation 

 is formed at this point in the cup. The arms are bifurcated, and 

 those on the posterior side are the strongest. 



