MONOGEAPH OF THE EXISTING CRINOIDS. 



273 



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

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

 into the form of a hook or spiral, exactly as do the cirri, formuig tondril-hko 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 moans of its cirri. 



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

 rouinded processes exactly resembling the dorsal convex swellings on the outer 

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



Fio. 314. 



Fig. 315. 



Fig. 316. 



Fig. 317. 



Fig. 318. 



Figs. 314-318.— 314, The extreme tip or a ctrrus from a specimen op Stepdanometra monacastiia from the Marshall 



ISLANPS (CAMERA LUCIDA DRAWING BY THE AUTHOR). 315, THE E.XIREME TIP OF A CIRRUS FROM A SPECIMEN OF IIaTIIRO- 

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

 A SPECIMEN OF LePTOMETEA PH.U.ANGinM FROM NAPLES (CAMERA LUODA DRAWING BY THE AUTHOR). 317, THE E.XTREME 

 TIP OF A CIRRUS FROM A SPECIMEN OF OuOOMETRA THETIDIS FROM NEW SoUTH WALES (CAMERA LUCIDA DRAWING UY THE 

 AUTHOR). 31S, The extreme tip of a CIRRUS FROM A SPECIMEN OF HiMEROMETRA PERSICA FROM THE PEESIAN OCL? 

 (CAMERA LUaDA 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; tliat is, while the axial canal in the pinnules progres- 

 sively moves dorsalward so that it comes to lie nearer and nearer the dorsal surface, 

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

 nearer ami nearer the ventral surface. 



