MONOGRAPH OF THE EXISTING CRINOIDS. 



127 



Fig. 69. 



Fig. 70. 



Fro. 73. 



Fio. 74. 



Figs. 69-74.— 69, Perforated plates from the skin of Caudina plan.u>etura, showdjo a close approximation to the 



PRIMITn'E TYPE OF ECIUNODERMAL CALCIFICATION (.IFTER 11. L. CLARK). 70, A PERFORATED PLATE FROM THE SKDJ OF CaU- 

 DINA CALIFORNICA, SHOWING INCIPIENT CALCAREOUS RODS (.iFTER H. L. CLARK). 71, THE APICAL .SYSTEM OF A YOCNO 

 SPECIMEN OF EUROCIDARIS NUTRI.X FROM THE ANTARCTIC, SHOWING THE PRIMITIVE CENTRAL PLATE SURROUNDED UY TIVE 

 GENITALS (CORRESPONDING TO THE CEINOID BASALS), BEYOND WHICH ARE FIVE OCULARS (COREESPONDrNO TO THE CRIHOID 

 INFRABASALS). T2, THE APICAL SYSTEM OF A SPECIMEN OF LYTECHINUS VAEIEGATUS FROM FLORIDA, .SHOWING THE CENTRAL 

 PLATE RESOL%'ED INTO NUMEROUS SMALL PLATES AND SURROUNDED BY Fn-E GENITALS (CORRESPONDING TO THE CRINOID 

 BASALS), BEYOND WHICH ARE FIVE OCULARS (CORRESPONDING TO THE CRINOID INFRABASAU<), THE TWO POSTERIOR REACHINO 

 THE PERIPROCTAL AREA BETWEEN THE GENITALS; THE MADREPORIC PORES ARE NOT CONFINED TO THE RIGHT ANTERIOR 

 GENITAL, BUT OCCUR ALSO ON THE TWO ADJACENT OCULARS. 73, TllE APICAL SYSTEM OF A SPECIMEN OF ARBACIA STELL.4TA 



FROM Margarita Island, Lower Oalifornha, showing the central plate divided into fouh, and the right anterior 



GENITAL, ordinarily A MADREPORIC PLATE, RESOLVED INTO NUMEROUS SMALL PLATES. 74, DIAGRAMS ILLUSTRATING TUB 

 progressive CHANGES DURING GROWTH IN THE RELATIONSHIPS OF THE ELEMENTS OF THE CALY.\, A.ST> IN HIE REUTION- 

 SHIP BETWEEN THE CALYX AND THE VISCERAL MA.S3 OF A COMATULID: THE EXTREME ATTAINED BY THE ADULT PENTACRINITE 

 IS REPRESENTED BY E; THE PLATES SHOWN ARE THE BASALS, THE RADIALS, AND THE ORALS. 



