MONOGRAPH OF THE EXISTING CHIXOIDS. 



93 



FIG. 66. 



FIG. 67. 



FIG. 68. 



FIGS. 66-68. 66, A CROSS SECTION THROUGH THE CENTRODORSAL AND RADIAL PENTAGON Of A SPECIMEN OF PENTAMETROCRINUS 

 JAPONICUS FROM SOUTHERN JAPAN, SHOWING THE VARIOUS CAVITIES AND CANALS AND ILLUSTRATING A TYPICAL MACROPI111KATE 

 FORM. THE STRUCTURE IS, IN GENERAL, THE SAME AS THAT OF FLOROMETRA ASPERRIMA (FIG. 67); THE CENTRAL CAVITY IN THE 

 CENTRODORSAL IS LARGER, AND THE ROSETTE IS SOMEWHAT MORE DORSAL IN POSITION; THERE IS THUS NO KOOM FDR THE 

 RADIAL WATER VESSEL BENEATH THE CANAL LODGING THE A.XLIL CORD, BUT THE INTERRADUL WATER VESSEL, OX TIIK HTIIKIl 

 SIDE OF THE FIGURE, IS LARGER; THE REENTRANT ANGLE ON THE RIGHT SIDE, REPRESENTING THE DORSAL UGAHENT FOSSA 

 CUT ACROSS, IS NOT SO DEEP AS IN FLOROMETRA ASPERRIMA. THE MIDRADIAL SECTION (LEFT-HAND SIDE) PASSES JUST 

 PROXIMAL TO THE MIDDLE OF THE RADUL; THE INTERMUSCULAR SEPTUM IS SEEN RUNNING TO THE OPENING OF THE CANAL; 

 THE DEPTH OF THE MUSCULAR FOSS.E IS SHOWN BY THE TUBULAR OUTER PORTION OF THE CANAL. 67, A CROSS .SECTION- 

 THROUGH THE CENTRODORSAL AND RADIAL PENTAGON OF A SPECIMEN OF FLOROMETRA ASPERRIMA FROM ALASKA, SHIIWINi; 

 THE VARIOUS CAVITIES AND CANALS AND ILLUSTRATING A MACROPHREATE FORM WHICH HAS ASSUMED MANY OUGOPHREATE 

 CHARACTERS. THE DIVIDING LINE BETWEEN THE CENTRODORSAL AND THE RADL\L PENTAGON IS INDICATED BY A SERIES OF 

 SHORT PARALLEL LINES DENOTING A SYNOSTOSIS; THAT ON THE EIGHT IS LOW, AS IT PASSES THROUGH A MIDRADIAL PLANE; 

 THAT ON THE LEFT IS HIGH, AS IT CUTS THROUGH TIIF. INTF.RRADIAL ANGLE WHERE THE VENTRAL SURFACE OF THE CENTRO- 

 DORSAL RISES INTO A RIDGE. THE CENTRAL CAVITY INCLOSING THE CENTRAL CAPSULE IS SHOWN WITHIN THE CENll:i>l>l:SAl.; 

 FOUR CIRRUS VESSELS LEADING FROM IT ABE CUT LONGITUDINALLY; VENTRALLY THE CENTRAL CAVITY IS IIOVNDKU P.Y THE 

 ROSETTE, A THIN LOBATE PLATE SHOWN HERE CUT ACROSS THE MIDDLE. IN THE RADLIL ON THE RIGHT, Wllli II IS rl 

 TUDDJALLY ALONG THE DORSOVF.NTRAL PLANE, IS SHOWN THE BLIND END OF THE KADIAL WATER TUBE AND, ABOVE IT, THE 

 AXIAL CANAL INCLOSING THE DORSAL NERVE OF THE ARM; IN THE RADIAL TO THE LEFT, THE LATERAL FACE OF WIIK II IS 

 EXPOSED, IS SEEN THE CANAL LODGING THE RADUL CO.MMI i A CRuSS SFATH'N THROUGH THE CENTRODORSAI. AND 



RADIAL PENTAGON OF A SPECIMEN OP COMANTHUS PINGUIS FROM SOUTHERN JAPAN, SHOWING THE VARIOUS CAVITII B \M> 

 CANALS AND ILLUSTRATING A TYPICAL OLIGOPHREATE FORM. TlIE DETAILS MAT BE READILY UNDERSTOOD BY COMPARISON 

 WITH THE FIGUHE OF A SIMILAR SECTION OF FLOHOMETRA ASPERRIMA (FIG. 67); THE LINES MARKING THE SYNOSTOSIS 

 BETWEEN THE RADIALS AND THE VENTRAL SIDE OF THE CENTRODORSAL ON THE LEFT ARE LONGER THAN Tlirisr. ON Til ' 

 INDICATING THE PRESENCE OF A BASAL RAY; THE CENTRAL CAVITY IN THE CENTRODORSAL HAS BECOME VERY SHALLOW; AND 

 THE CENTRAL CAPSULE HAS BECOME DISPLACED VENTRALLY, SO THAT IT LIES LARGELY WITHIN THE RADIAL PENTAGON INSTEAD 

 OF ENTIRELY WITHIN THE CENTRODORSAL, AS IN TYPICAL MACP.OPHREATF. FORMS; THE Ili'SETTE LIES DEKI'LY WITHIN TUB 

 DORSAL SIDE OP THE RADIAL PENTAGON. THE FUNNEL-SHAPEH SPACE WITHIN THE RADIAL Fi:NT\M'N IS FILLED WITH A 

 LOOSE CALCAREOUS NETWORK, FORMING THE CENTRAL PLUG. 



