Yerrill, N'otes on Radlata. 299 



sides unite together for a short distance so that the ocular plates do 

 not join the anal area ; the niadreporic plate is much larger than the 

 others. The anal area is broad-oval, its four plates usually promi- 

 nent. The ambulacral zones are, ordinarily, somewhat elevated and 

 in some cases considerably so, giving a somewhat pentagonal foim 

 to the outline of the test. They bear two regular rows of tubercles, 

 nearly as large as the interambulacral beneath and on the sides, but 

 becoming very small above and disappearing before reaching the 

 summit. Interambulacra with large naked median spaces, extending 

 about half-way to the periphery ; sutures between the plates rather 

 deep and conspicuous. The plates are very broad, fifteen forming 

 each vertical series in the specimen above measured. The tubercles 

 are very large on the sides, forming six vertical rows, which are not 

 crowded. The two middle rows are represented at the periphery by 

 a few tubercles only ; the two next extend from the actinal area to 

 within about five plates of the summit ; the outer row on each side 

 continues even to the ocular plates, but the two or three upper tubercles 

 are much smaller than the lateral. Actinal area sub-pentagonal, the 

 cuts shallow. Auricles short and broad, the supports widely separa- 

 ted at the ends. 



Color of test, in dried specimens, grayish or purplish brown, 

 weathering to purplish white or rose-color ; the lower half or the 

 whole of the outer end of the interambulacral plates deep purple, in 

 the naked spaces of the upper surface, forming a doul^le series of 

 conspicuous, alternating, angular spots ; genital plates variegated 

 with purple ; spines dark purple. 



A specimen 1*35 inches in diameter of test has but eleven interam- 

 bulacral plates in the vertical series and but four rows of large 

 interaml )ulacral tubercles, with a very few belonging to a fifth row. 

 In this the auricular supports are short, broad at the ends, where they 

 are in contact or overlap. 



Specimens "4 in diameter have but eight plates in the vertical series. 

 The outer row of interambulacral tubercles reach the summit, but 

 the intervening rows are represented only by three or four irregularly 

 placed tubercles on the lower sui-face. The spines are mostly flat- 

 tened and channeled at the ends, the longest equaling the diameter 

 of the test. Sutures more marked than in the large examples. 



An examination of a large number of specimens of all ages and 

 from various localities has convinced me that the JE. stellata of Agas- 

 siz is the same as E. incisa A. Ag. Dr. Ltitken's work was printed 

 before he had received that of Mr. Agassiz. He has suggested that 

 his species might prove identical with E. stellata. 



