THE CRINOIDEA 179 



(1887), Ordovician, Canada; x rests on post. B, RA immediately above 

 r. post. B ; r. post. Rs is above general level of RR and may be IBr r These 

 two genera suggest that RA of Dicyclica may not be strictly homologous 

 with RA of Monocyclica. Dendrocrinus, Hall (1852), Ordovician and 

 Silurian, N. America ; large anal sac with folded plates making wide anal 

 area in cup (see also Fig. XXVI. 2, 3). Homocrinus, Hall (1852, em. 

 Bather, 1893), Silurian and Devonian, N. America and Europe ; RA 

 rhomboid and smaller. Thenarocrinus, Bather (1890), Silurian, England ; 

 large sac, anal area widened by RA sinking between BB. FAMILY 2. 

 BOTRYOCRINIDAE. Dendrocrinoidea with arms bifurcating in two main 

 rami with armlets or pinnules ; RA usually small and quadrangular 

 or absent. This family connects Dendrocrinidae with Decadocrinidae, 

 and it is difficult to diagnose it so as to include all of the closely 

 related forms. Genera Botryocrinus, Angelin (1878, em. Bather, 1891 ; 

 syn. Sicyocrinus, Ang.), Silurian and Devonian, Gotland, England, Canada ; 

 small RA, large anal sac, often coiled ; arms range from irregularly 

 dichotomous, through ramuliferous, to pinnulate (Fig. XCVIL, see also 

 Figs. III., XIII., and XXL). Gothocrinus, Bather (1893), Silurian, Gotland, 

 has a cup like Dendrocrimis with ramuliferous arms. Mastigocrinus, 

 Bather (1892), Silurian, England, has very long, finely dichotomous arms, 



FIG. XCVII. FIG. XCVIII. 



Analysis of cup in liotryocrinus. Analysis of cup in Atelestocrlnus. 



no RA (for anal sac, see Fig. XLVIIL). Gastrocrinus and Rhadinocrinus, 

 Jaekel (1895), Devonian, Germany, are, respectively, like a Botryocrinus 

 with cirri in whorls of 5 (Fig. XVII. 1), and a Gothocrinus with minute 

 ramules. Cosmocrinus, Jaekel (1898), Devonian, Germany and N. America, 

 has broad cup of Botryocrinus type, arms pinnulate, and with ramuli on the 

 inner side of the two main rami. Vasocrinus, Lyon (1857, em. W. & 

 Sp., 1879), Devonian to Carboniferous, N. America, scarcely differs from 

 Botryocrinus. Barycrinus, Meek & Worthen (1868, em. W. & Sp., 1879), 

 Carboniferous, N. America and England, has heavier cup-plates and large 

 stem-lumen. Goniocrinus, Miller & Gurley (1890), Waverly Group, 

 Iowa, has no RA, and has cirri like Gastrocrinus, Atelestocrimis, W. & Sp. 

 (1886), Carboniferous, N. America, is distinguished by absence of an arm 

 from ant. R; large RA supporting rt (Fig. XCVIII.) ; arms ramuliferous. 

 Streptocrinus, W. & Sp. (1886; redescr. Bather, 1893 ; syn. Ophiocrinus, 

 Ang. non Salter), has branched arms, coiling inwards, with pinnule-like 

 processes arising irregularly from sides of Br ; no RA, anal sac coiled. 

 FAMILY 3. LOPHOCRINIDAE. Dendrocrinoidea with only 1 ramus to each 

 arm, with ramuli springing from the alternate sides of every second Br ; 

 with no RA, but x supporting on its shoulders 2 plates of a delicate 

 anal sac. Genus Lophocrinus, H. v. Meyer (1858 ; redescr. Jaekel, 

 1895 ; syn. 1 Carduocrinus, v. Koenen), Upper Carboniferous, Germany. 



