REPORT ON THE ECHINOIDEA MORTEN SEN 281 



The ambulacra are nearly straight. The interporiferous zone is 

 about twice the width of the pore zone. The marginal series of 

 tubercles is regular, the tubercles rather small, not contiguous. 

 Within the marginal tubercle each plate carries a small tubercle at 

 the lower edge, the rest of the plate being smooth and rather sunken. 

 The horizontal sutures are slightly deepened, but it can not be said 

 that the grooves are distinct; rather the} 7- go together with the whole 

 of the sunken median part. In places there is a small tubercle 

 between the marginal tubercles. The pores are small, equal sized, 

 separated only by a narrow wall which is scarcely raised. The 

 ridge between the adjoining pore pairs is rather low (pi. 74, fig. 3). 



In the interambulacra the areoles not very deep, the 3 or 4 proxi- 

 mal ones confluent; only the lowermost are slightly transverse-oval. 

 The scrobicular ring is not very conspicuous, the 

 tubercles being scarcely larger than the marginal 

 ambulacral ones. Outside the scrobicular ring 

 there are only a few secondary tubercles, the me- 

 dian part of the plates being otherwise naked and 

 somewhat sunken. The horizontal sutures are 

 deepened so as to form rather conspicuous grooves. 

 There is no indication of grooves at the adradial 

 end of the sutures, and the scrobicular tubercles 

 leave no naked portion on the adradial side of the 

 plates. The horizontal sutures between the upper 

 areoles are not deepened. The median part of the 

 interambulacra is about as wide as an areole. 



. , . i i i c i i • i FlG - 17.— Part of apical 



I he apical system is exactly hall the horizontal system of schizocid- 

 diameter and is rather elevated. The ocular plates ARIS FASCIATA . new 

 are narrowly insert. The whole apical system is 

 covered, though not very closely, with small tubercles of uniform size. 

 The genital pores are not yet developed (fig. 17). The peristome is 

 of the same size as .the apical system, and is slightly elevated. There 

 are 7 or 8 ambulacral plates in a series; the ambulacra join at the 

 mouth edge so as to exclude the interradial plates from the mouth 

 edge. There are 2 or 3 of the latter in each interradial space. 



The longest ambital spines are nearly twice the horizontal diame- 

 ter. They are nearly cylindrical, tapering only very slightly toward 

 the point which is broadened into a small crown. At the base there 

 are a few larger spinules, placed mainly at the sides; they do not unite 

 so as to form a disk. Otherwise the spine is covered by rather nu- 

 merous smaller spinules, arranged fairly distinctly in longitudinal 

 series. As usual the spinules are smaller on the adoral than on the 

 adapical side of the spiue. The surface of the spine is otherwise 



