PART 5 



FOREWORD 



XIII 



measurements and inserted them in the descriptions in the hope that they will assist 

 in comparisons with other material, and that their use will be adopted by others in the 

 future to complement such measurements as the arm and cirrus length, already in use. 

 As for the illustrations to this part, it was decided that the inclusion of photo- 

 graphic plates is not justified for crinoids, more particularly for the almost uniformly 

 10-armed Antedonidae, many of which are superficially quite similar. Instead, line 

 drawings have been substituted and these are supplemented by figures of species 

 given in parts 1 and 2 of this work, and included systematically in this final part. Apolo- 

 gies are due for the relative inversion of my figures of centrodorsals and calyces. In 

 drawing I tend to align comatulids with the dorsal side uppermost and the centrodorsal 

 with its base towards the bottom, whereas Mr. Clark sees the whole oriented as in 

 life, with the centrodorsal downwards. 



distal 



anterior 



interior exterior 



basa I 



prox i ma I 



ven tra I 



upper 



peripheral 



distal 

 dorsal / 

 Jower/ a P' cal 



pos tenor 



Another confusion which I found on coming fresh to the study of crinoids lay in 

 the orientation of some of the terms used in description. 'Proximal' and 'dishd' are 

 clear enough but 'anterior' and 'posterior' need some 'clarification for a radially sym- 

 metrical animal, particularly as Mr. Clark uses thorn in two distinct plains. One of 

 these is across the disk, the radius and corresponding arm or arms opposite the anal 

 interradius being anterior, while the other anus arc right and left anterior or posterior. 

 The second plane extends along the lengths of all the arms, the tips being anterior. In 



