i;o THE CRINOIDEA 



anus at distal end ; small and eccentric ; Amb visible in tegmen, either 

 as two rows of large covering-plates which pass out from between and 

 follow the branching of the food-grooves, or as large single plates (lAmb 

 and IIAmb), succeeded by small covering-plates, which pass on to the free 

 arms. Steganocrinus, Meek & Worthen (1866), differs from Actinocrinus 

 in the extension of each ray into 1 or 2 rigid tubular rami, from 

 which biserial ramuli are given off alternately on opposite sides, either 

 from every ossicle or from every other ; covering-plates consist of side- 

 pieces and spinous Amb. Cactocrinus (W. & Sp., 1897) differs from 

 Actinocrinus in having the arm-rami given off in a continuous row 

 around the theca, the brachials meeting laterally, so that iBr are not in 

 contact with iAmb (cf. Eutrochocrinus) ; bifurcation takes place on each 

 successive plate, i.e. all Br, except the finials, are axillary ; all pinnulars, 

 except the extreme distal ones, bear hooks which imbricate over the adjacent 

 pinnules (cf. structure of a feather) ; covering-plates consist of side-pieces 

 and Amb ; Br and tegminal plates spinous (cf. Fig. XLIV.). Teleiocrinus, W. 

 & Sp. (1881 ; syn. Calatliocrinus, Hall, pars, non v. Meyer) ; a modified 

 Cactocrinus in which the arms have become so numerous and crowded 

 that they are pushed outward, while their bases have become united 

 and extended as a broad rim at the top of the theca ; between the Amb 

 and iAmb forming the roof of this rim, and the Br forming its floor, are 

 developed processes of stereom serving as girders ; the ambulacra with 

 their ambulacrals are mostly depressed below the tegmen and covered by 

 iAmb ; a respiratory pore is at the side of each ambulacral opening into 

 the theca. Physetocrinus, Meek & Worthen (1869), differs from Actino- 

 crinus in the absence of an anal tube, and in bifurcation of arms on each 

 successive Br, as in Cactocrinus. Strotocrinus, Meek & Worthen (1866), 

 often confounded with Teleiocrinus, towards which it is convergent, bears 

 to Physetocrinus precisely the same relation as Teleiocrinus bears to Cacto- 

 crinus. Sampsonocrinus, Mill. & Gurl. (1895), Carboniferous, Missouri, 

 has r. and L post. iBr truncating BB, and only 1 IBr in r. and 1. ant. radii ; 

 the unique specimen is best regarded as an abnormal Actinocrinus. Com- 

 pare Phillipsocrinus, M'Coy (1844 or 1862), Carboniferous, Ireland, in 

 which also some iBr truncate BB ; but since BB are here 4, this may 

 be a more direct descendant of Xenocrinidae, perhaps by way of the 

 Silurian Laubeocrinus, Waagen & Jahn (1899), which seems a link 

 between early Batocrinoidea and Actinocrinoidea. FAMILY 2. AMPHORA- 

 CRINIDAE. Actinocrinoidea with cup depressed and tegmen much elevated, 

 accompanied by downward projection of proximal regions of arm-rays ; 

 cup-plates with granule -vermicular ornament; iBr few; in other 

 respects like Actinocrinidae. Genus Amphoracrinus, Austin (1848), 

 Carboniferous, Europe and N. America ; arms free from lax or IIBrj ; 

 anal tube short and eccentric. Two American species occasionally have 

 3 plates (instead of 2) succeeding the proximal anal, but the middle of 

 these is small and wedge-shaped, barely touching the anal ; this may be 

 a plate of the ensuing row pressed down, or it may represent the middle 

 plate in Batocrinoidea. 



