CRINOIDEA. 301 



and 5 x 2-3 primibrachials (with 5 small infrabasals in Extracrinus). 

 Arms divided 1-10 times, with pinnules. Calyx cover membranous, 

 containing thin loose plates. Without orals in adult. Stalk long, penta- 

 gonal, rarely cylindrical, with whorls of cirri, without root-like processes ; 

 two joints are united by syzygyat each node, of which the upper bears the 

 cirri. Triassic to present time. Pentacrinus Miller (Isocrinus v. Meyer 

 1837) (Fig. 208), the 2nd primibrachial is axillary. Triassic to present 

 time, P. asterius L. (caput medusae Mill.), Caribb. Sea, 120 fms. ; P. 

 miilleri Oerst, W. Indies 50-531 fms. ; P. wyville-thomsoni Jeffreys, 

 800-1,100 fms. Extracrinus Austin (Pentacrinus Blum. 1837,) f- Metacrinus 

 P. H. Carp., recent, Pacific. Balanocrius Ag., f. Dadocrinus v. Meyer, Trias. 



Fam. 6. Gomatulidae. In the young state stalked, later unstalked 

 and freeswimming. Calyx composed of a centrodorsal plate with cirri ; 

 infrabasals visible only in larva, fused with centrodorsal (top stem-segment) 

 in adult ; 5 more or less reduced basals, which may be visible externally or 

 hidden, 5 radials, and 5. X 2 or more primibrachs. Interradials absent. 

 Calyx-cover membranous, rarely with thin plates. Orals absent in 

 adult. Arms simple or branched, with pinnules, brachials alternate. 

 More than 150 living species, mostly in shallow water. Lias to present 

 time. Antedon Fremink. (Comatula Lmk. etc. ) (Fig. 188). Arms fork once or 

 more, the second primibrach axillary, Lias to present time ; Eudiocrinus 

 P. H. Carpenter, 5 undivided arms, f. and r. Pacific and Bay of Biscay, 

 50-900 fms. Actinometra Miiller, mouth excentric, Jura to present time, 

 most seas, littoral to 800 fms. Atelecrinus P. H. Carp., with basals visible 

 on outside of calyx, r, trop. Atl. and Pac. Promachocrinus P. H. Carp., 

 with 10 radials (basals 5), recent. Pacific and S. Sea, 70 to 1,800 fms. 

 Thiolliericrinus Etallon, Jura and Chalk. 



The position of Tliaumatocrinus P. H. Carpenter (one specimen only, 

 S. Sea, 1,800 fathoms) is very uncertain. It is unstalked, has a calyx 

 composed of a centrodorsal with cirri, 5 basals, 5 radials and 5 inter- 

 radials which touch the basals, the anal interradial carries a tapermg 

 4-jointed process ; 5 arms, unbranched with pinnules ; mouth central 

 with 5 large orals separated from the edge of the calyx by 2 or 3 rows of 

 small irregular plates. In the separation of its radials laterally by inter- 

 radials it recalls the Camerate family Rhodocrinidae. In Reteocrinus and 

 Xenocrinus, of the same order, the radials are separated by a number of 

 small interradials. In some recent Crinoids interradials are present but 

 always above the radials ; they are therefore interprimibrachs, etc. In 

 the structure of its calyx and in the entire freedom of its arms, it resembles 

 the Larviformia. 



The following families may be mentioned here, though where they 

 should be really placed in the system is a difficult question. 



Fam. Eugeniacrinidae. Calyx composed of 5 (rarely 4) thick, firmly 

 connected radials ; basals are absent and the calyx cover is not known. 

 Stalk short, composed of long, cylindrical broad joints, without cirri. Axial 

 canals are present, and the basals are probably covered by the radials. 

 Lias, Jurassic and lower Cretaceous of Europe. Eugeniacrinus Miller, 

 Eudesicrinus Loriol, Tetracrinus Miinst., Phyllocrinus d'Orb. 



Fam. Plicatocrinidae. Calyx composed of 4, 6, or 8 (rarely 5 or 7) 

 high, thin radials and of a 4- to 6-sided undivided base. Cavity of cup 

 wide and deep. Calyx cover unknown. The radials carry an axillary 

 primibrach from which 2 unbranched arms arise. Stalk thin with long, 

 cylindrical joints. Plicatocrinus Miinst. Upper Jurassic. 



