550 THE ATLANTIC. [CHAP. Vv. 
the bottom of a deep anterior groove; and nearly the whole of 
the dorsal surface is occupied by a depression beneath which the 
anterior ambulacral canal runs, sending up through a petaloid 
arrangement of two double rows of pores two series of tube 
feet with very large flower-like terminal disks, the disks sup- 
Fia. 95.— Aceste bellidifera, Wyvitte Tuomson. A. Upper surface; B. Under surface. 
Twice the natural size. (No. 44.) 
ported by an elegant star of calcified tissue. The four paired 
ambulacra are slightly marked compared with the odd ambula- 
crum, a slender tube running under the ranges of ambulacral 
plates and giving off simple processes to single pores. The ex- 
cretory opening is at the posterior extremity ; only two ovaries 
are developed, and the eggs appear to be very large at the time 
of expulsion, corresponding with the great size of the ovarial 
openings. The apical plates are arranged in the usual way, and 
not “disjunct,” as in Powrtalesia, which might seem to indicate 
a wide difference between the two genera; but I am inclined 
to think that the weight of resemblances is in favor of their 
approximation. In this species there is a singular ingrowth of 
the plates of the perisom which causes them to overlap, and 
