MONOGRAPH OF THE EXISTING CRINOIDS. 



93 



Fio. 66. 



riG. 67. 



Fig. 6S. 



Figs. 66-68. — 66, .V cross sectiox through the centrodoksal axd radial pentagon of a specimen op Pentametrocrinus 



JAPONICDS from southern JaPAN, SHOWING THE V.UUOUS CA\aTIES AND CANALS AND ILLUSTRATING A TYPICAL M.tCROPHREATE 

 FORM. The STRUCTURE IS, IN GENERAL, THE SAME AS THATOF FLOROMETRA ASPERROIA (FIG. 67); THE CENTRAL CAVin'rN THE 

 CENTRODORSAL IS LARGER, AND THE ROSETTE IS SOMEWHAT MORE DORS.^L IN POSITION; THERE IS THUS NO ROOM FOR THE 

 RADIAL WATER VESSEL BENEATH THE CANAL LODGING THE AXL\L CORD, BUT THE INTERR.UJLiL WATER \'ES.SEL, ON THE OTHErf 

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

 CUT ACROSS, IS NOT SO DEEP AS IN FLOROMETR.V ASPERROIA. THE MIDRADL\L SECTION (LEFT-HAND SIDE) PASSES JUST 

 PEO.XIMAL TO THE MIDDLE OF THE KADLAL; THE INTERMUSCULAR SEPTUM IS SEEN RUNNING TO THE OPENING OF THE CA.NAL; 

 THE DEPTH OF THE MUSCULAR FOSSiE IS SHO'«'N BY THE TUBULAR OUTER PORTION OF THE CANAL. 67, A CROSS SECTION 

 THROUGH THE CENTRODORSAL AND RADUL PENTAGON OF A SPECIMEN OF FLOROMETR.4 ASPERROIA FROM AlASK.1, SHOWING 

 THE V.\RI0U3 CAVITIES AND CANALS .AND ILLUSTRATING A MACROPHREATE FORM WHICH HAS ASSUMED M.\NY OUGOPHREATK 

 CHARACTERS. THE Dn'IDING LINE BETWEEN THE CENTRODORSAL AND THE RADIAL PENTAGON IS INDICATED BY A SERIES OF 

 SHORT PARALLEL LINES DENOTING A SYNOSTOSIS; TH.VT ON THE RIGHT IS LOW, AS IT PASSES THROUGH A MIDRADLAL PLANK; 

 THAT ON THE LEFT IS HIGH, AS IT CUTS THROUGH THE INTERRADIAL ANGLE WHERE THE VENTRAL SURFACE OF THE CENTRO- 

 DORSAL RISES INTO A RIDGE. THE CENTRAL CAVITY INCLOSING THE CENTRAL CAPSULE IS SUOW.N WITHIN THE CENTRODORSAL; 

 FOUR CmRUS VESSELS LEADING FROM IT ARE CUT LONGITUDINALLY; VENTRALLY THE CENTRAL CAVITY IS BOUNDED BY THE 

 ROSETTE, A THIN LOBATE PLATE SHOWN HERE CUT ACROSS THE MIDDLE. IN THE RADUL ON THE RIGHT, 'milCH IS CUT LONGI- 

 TUDINALLY ALONG THE DORSOVENTRAL PL.ANE, IS SHOWN THE BLIND EN'D OF THE RADIAL WATER TUBE AND, ABOVE IT, THE 

 AXIAL CANAL INCLOSING THE DORSAL NERVE OF THE ARM; IN THE R.VDUL TO THE LEFT, THE LATERAL FACE OF WHICH IS 

 EXPOSED, IS SEEN THE C.VNAL LODGING THE RADIAL COMMISSLTIE. 6.S, A CROSS SECTION THROUGH THE CENTRODORSAL ANT> 

 EADLIL PENTAGON OF A SPECIMEN OF COMANTHUS PINGUIS FROM SOUTHERN JAPAN, SHOWING THE VARIOUS CAVITIES AND 

 CANALS AND ILLUSTRATING A TYPICAL OUGOPHREATE FORM. THE DETAILS MAY BE READILY UNDERSTOOD BY COMPARISON 

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

 BETWEEN THE R.ADIALS AND THE VENTRAL SIDE OF THE CENTRODORSAL ON THE LEFT ARE LONGER THAN THOSE O.N THE RIGHT, 

 INDICATINC THE PRESENCE OP A BASAL RAY; THE CENTRAL CAVITY IN THE CENTRODORSAL HAS BECOME VERY SHALLOW; ANT> 

 THE CENTRAL CU-SULE HAS BECOME DISPLACED VENTRALLV,SO THAT IT LIES LARGELY WITHIN THE RADIAL PENTAGON INSTF_ID 

 OF E.VTtRELY' WITHIN THE CENTRODORSAL, AS LN TYPICAL MACROPHREATE FORilS; THE ROSETTE UES DEEPLY 'mTUIN THE 

 DORSAL SIDE OF THE RADIAL PENTAGON. THE FUNNEL-SU.VPED SPACE WITHIN THE RADIAL PENTAGON IS FILLED WITH A 

 LOOSE CALCAREOUS NETWORK, FOBMDtO THE CENTRAL PLUG. 



