74 
Fig. 6. Antedon petasus. 
a. showing a case of p3 developing into an arm. b. inner pi of left posterior radius, 
posterior arm, developed into an arm. c. dichotomously branched pi of right anterior 
radius, d. outer pi of left posterior radius, posterior arm, transformed into a small 
arm. e. another case of p3 developing into an arm. f. right anterior radius, anterior 
arm, w.th inner pi slightly branched, outer pi transformed into an arm. g. longi- 
tudinally divided epizygal joint. h. irregular armdivision. 
All the tlgures 6 /i. 
