1 88 



THE CRINOIDEA 



FIG. CVII. 



Analysis of cup in P.i/cnosoeciis. 

 (After Bather.) 



not interlock ; columnals solid, moniliform, alternating in thickness. 



Lecanocrinus, Hall (1852), Silurian and Devonian, N. America and Europe, 



differs only in greater smoothness of 

 cup and approximation of arms, 

 which may even interlock by the 

 alternating edges of the Br. Cyrtido- 

 crinus, Angelin (1878), only known 

 from cup, which appears to be like 

 that of Lecanocrinut, but is said to 

 have 4 BB. Clidochirus, Ang. (1878), 



Silurian, Gotland ; arms abut, but do not interlock ; no RA, but 3 anals 



in vertical series rest on truncate post. B. Mespilocrinus, de Koninck 



(1853), Lower Carboniferous, Belgium, England, and N. America, differs 



from last-mentioned in having each arm curved 



over to the right, so that they all fold with a 



sinistral twist (as seen from above) ; IBr x wedge- 

 shaped, broader on left. Nipterocrinus, Wachs- 



muth in Meek & Worthen (1868), Carboniferous, 



N. America, should perhaps come here. Ichthyo- 



crinus, Conrad (1842), Silurian, N. America and 



Europe, has no anals ; arms abut all round and 



interlock by edges of Br (Fig. CVIIL). FAMILY 2. 



GAZACKINIDAE. Impinnata (?) with a single large 



iBr in each interradius, the posterior (anal) resting 



on truncate edge of large post. B ; arms isotomous ; 



tegmen of 5 O of Cyathocrinoid type, surrounding 



a peristorne which is covered by fused proximal 



Amb, and supporting Amb along their edges ; 



food -grooves fork on the tegmen (Fig. CIX.). 



Genus Gazacrinus, S. A. Miller (1892 ; syn. 



FIG. CVIII. 



Iclitliyocrinus pirlformis, 



Idiocrinus. W. & Sp.), Silurian, N. America, is slightly restored from Brit. 



_, ., ~ . . , Mus. 40214. (Nat. size.) 



referred to the Camerate Family Dimerocrmulae 



by W. & Sp. (1897). Its dorsal cup does not differ essentially from that of 



Anisocnnus (infra), but the number of IBB is uncertain. The tegmen, 



HBrJ 



Gazacrinus. (Diagrammatised from Wachsmuth & Springer), x 2 diam. 1, G. inornatns, 

 tegmen with almost all ambulacrals removed. 2, G. ventricosus, dorsal view. 3, same, side 

 view, with proximal ambulacrals (P) in position. As, passage for rectum through posterior 

 oral ; v.g, ventral grooves passing between edges of orals. Other letters as usual. 



scarcely of either Flexible or Cainerate type, suggests recent descent from 

 'nadunata. FAMILY 3. TAXOCRINIDAE. Impinnata with iBr, which usually 



