258 
The single madreporic plate is situated outside the very wide 
mouth frame, on the short, nearly vertical edge connecting the 
ventral and the dorsal side. In this part are also found the short 
genital slits; neither can he seen from the ventral side. 
The whole animal, both disk and arms, is covered by a fine, 
uniform granulation, which gives the skin quite a leatherlike ap- 
pearance. No larger tubercles occur, either on the disk or the 
arms. On the under side of the disk the grains are slightly larger. 
The radial shields form very broad ridges, separated only by quite 
narrow sunk lines; the whole dorsal side of the disk thus somewhat 
resembles a great fiower with ten large, flat petals. The disk 
passes rather evenly into the dorsal side of the arms, the radial 
shields being only slightly elevated at their outer edge. The limit 
between disk and arms is, however, more distinet than in A. tuber- 
culosus. 
The arms are exceedingly broad and robust, and the distances 
between the forkings are very short. The angles between the 
branches are sometimes nearly right, which results in the arms 
partly covering one another, for want of room. They are upon the 
whole low and rather flattened; the underside is flat, slightly hol- 
lowed along the middle line, the upper side is rounded. The outer 
branchlets are fine and of the usual Euryalid appearance; they 
may begin from about the 6th forking. Some of the arms, how¬ 
ever, have no sucli fine twigs at all, the tips of the branches 
being quite short and involuted. This is the case not only in such 
arms which are evidently regenerated and not vet fully grown out, 
but also in arms which show no trace of being regenerated and 
are as long as those with the fine twigs. In the same arm one 
main branch may end in the fine branchlets, while the other has 
the tips stout and involuted — even in the same main branch 
both forms may occur. This peculiar dimorphism of the arms thus 
appears to be a normal character of this species. 
The first forking is close to the edge of the disk, at the 
7th-8th joint. The first branches are very short, only 10-20 mm 
