1 7 6 



THE CR1NOIDEA 



or fan articulated to the R by a single IBr (Fig. XCI., see Bather, 1898). 

 FAMILY 7. CROTALOCRINIDAK. Cyathocrinoidea with cup as in Gyatho- 

 crinus ; anal tube when present constructed like that of Gissocrinus ; 

 tegmen almost entirely composed of Amb, some of which are much 

 modified ; the orals seem to have been covered by these and to have 

 atrophied, except post. O, which remains as a conspicuous plate, ap- 

 parently madreporic (Fig. XCII. 3) ; the entry of Amb into the tegmen is 

 connected with the shortening up of proximal portions of arms, so that 

 IBr, IIBr, IIIBr, and sometimes IVBr, all partially rest on R, and are 

 firmly united by suture with it (Fig. XCII. 1). Arms repeatedly iso- 

 tomous ; axial canal distinct, except sometimes in extreme distal region. 



IR 



VBr, 



ac. 



Fin. XCII. 



Crotaloctinidae. 1 and 2, Enattocriniis scriptus (after Wachsm. & Spr.). 1, posterior view 

 of cup and arm-bases. 2, enlarged view of more distal portions of anus ; a from side, b from 

 back, showing cornice-like projections. 3, tegmen of Crotalocriniis pulclier, from a specimen at 

 Stockholm. The arm-branches are united by the lateral processes of the brachials, the spaces 

 between being represented in solid black ; the interradii (IR), along which adjacent arms unite, 

 appear as five depressed lanceolate areas, in the posterior of which lies the short anal tube (A*) ; 

 the axial canals (a.c) are separate from the ventral grooves (v.g)', the latter are protected by 

 covering-plates (c.?<), which become larger towards the centre, and four proximal ones (P) meet 

 around the madreporite (M), x 2 diam. 



Stem large, round, with wide lumen (Fig. L. 1, 3, 4). All Silurian. 

 Genera Enallocrinus, d'Orbigny (1850), Gotland and England ; arm- 

 branches distinct, often with a pronounced cornice at distal margins of Br 

 (Fig. XCII. 2), in this as in other respects closely resembling Gissocrinus. 

 Crotalocrinus, Austin (1842 ; syn. Anihocrinus, Muller, 1853), Gotland, 

 England, and N. America ; arm-branches united by lateral processes from 

 each Br, so as to form a flexible network, which may be continuous all 

 round the crown, or divided into 5 broad arm-fans. The family is referred 

 to the Camerata by Wachsmuth and Springer (188 8); but the resemblance 

 to Marsipocrinus is homoplastic, and the connection with Cyathocrinidae 

 scarcely admits of question. The Crotalocrinidae might be called the 

 Adunata of the Dicyclica, just as Platycrinus and its allies are of the 

 Monocyclica. FAMILY 8. CODIACRINIDAE. Cyathocrinoidea with no anal 



