MONOGRAPH OF THE EXISTING CRINOIDS. 



273 



very gradually so that they are much stouter than the delicate grooved pinnules; 

 at first they lie horizontally, but in their distal third or half they curve dorsally 

 into the form of a hook or spiral, exactly as do the cirri, forming tendril-like attach- 

 ments all along the arm whereby the animal fixes each arm securely to the organisms 

 en the sea-floor in addition to fixing its central portion by means of its cirri. 



The segments of the stout grooveless pinnules are produced dorsally into blunt 

 rounded processes exactly resembling the dorsal convex swellings on the outer 

 cirrus segments; these arc perfectly smooth with no trace of spines. These pro- 



FlG. 314. 



FIG. 315. 



FIG. 316. 



FIG. 317. 



Flo. 318. 



FIGS. 314-318. 314, THE EXTREME TIT or A CIRRUS FROM A SPECIMEN OF STEPHANOMETRA MONACAXTHA FROM THE MARSHALL 

 ISLANDS (CAMERA LUCIDA DRAWING BY THE AUTHOR). 315, THE EXTREME TIP OF A CIRRUS FROM A SPECIMEN OF HATHRO- 

 METRA SARSn FROM NORWAY (CAMERA LUCIDA DRAWING BY THE AUTHOR). 316, THE DISTAL PORTION OF A CIRRUS FROM 

 A SPECIMEN OF L.EPTOMETRA PHALANGIUM FROM NAPLES (CAMERA LUCIDA DRAWING BY THE AUTHOR). 31", TlIE EXTREME 

 TIP OF A CIRRUS FROM A SPECIMEN OF OUGOMETRA THETIDIS FROM NEW SOUTH WALES (CAMERA LUCIDA DRAWING BY THE 

 AUTHOR). 31S, THE EXTREME TIP OF A CIRRUS FROM A SPECIMEN OF UlMEROMETRA PERS1CA FROM THE PERSIAN GULF 

 (CAMERA LUCIDA DRAWING BY THE AUTHOR). 



cesses are entirely absent from the dorsal side of the slender grooved pinnules which 

 instead, bear on the terminal segments the long recurved spines characteristic of 

 all the species of this family. 



The course of the axial canal in the cirri is just the reverse of the course of the 

 axial canal in the pinnules; that is, while the axial canal in the pinnules progiv<- 

 sively moves dorsalward so that it comes to lie nearer and nearer the dorsal surfu<-<>, 

 the axial canal in the cirri progressively moves vcutralward so that it comes to lie 

 nearer and nearer the ventral surface. 



