Boone, Echinodermata,- Cruises of "Eagle" and "Am," 1921-28 133 



Material examined : Ten very young specimens collected at Bury 

 Island, British West Indies, January 19, 1925, by the "Ira," Cat. 

 no. 268. Two small urchins, Porto Padre, Cuba, March, 1928, Cat. 

 no. 269. 



Color: This urchin, which may attain a diameter of five to six 

 inches, in life has the spines straw color or creamy, brownish yellow 

 at the base. The median interambulacral region is spotted with black, 

 the color of the heads of the numerous pedicellariae found all over 

 that region. When the suckers are fully expanded they form lighter 

 bands intermediate between the black bands of the median inter- 

 ambulacral region. 



Life history: The larval forms of this species were studied and 

 reported by Dr. Th. Mortensen. 



Habits: The young urchins spend the greater part of their time 

 concealed among and under rocks. The older urchins appear to prefer 

 an open grassy bottom. 



Technical description: Test large, sometimes attaining a width 

 diameter of six inches ; thin, in a specimen from Nassau measuring 

 80 mm. diameter the interambulacral space has twelve vertical rows 

 of primary tubercles, these are arranged on each plate more in hori- 

 zontal series ; towards the median line which is more or less bare from 

 the ambitus to the abactinal pole, the coronal plates are covered by 

 miliaries. The third and fourth vertical rows from the poriferal 

 zone are the most prominent and the only two extending to the 

 abactinal system. The tubercles are usually uniform. On the lower 

 surfaces of ambulacral and interambulacral regions the tubercles are 

 uniform and closely crowded in concentric rows around the actino- 

 stome as a center. In the median ambulacral region there are five ver- 

 tical rows of tubercles, more or less distinct, decidedly so at the 

 ambitus, the middle row indefinite, the exterior rows more prominent ; 

 these tubercles also tend to arrange in horizontal series. The vertical 

 lines of pores are separated by two to three irregularly arranged 

 vertical rows of small, secondary tubercles. The abactinal system is 

 distinctly marked; the madreporic body is larger than the others. 

 The large anal system is covered by a relatively small number of 

 plates of a nearly uniform size with a very few smaller plates imme- 

 diately surrounding the anus, each plate carrying only one or two 

 small, secondary tubercles and a very few miliaries. The genital ring 

 has but few secondary tubercles, they are few on the ocular and 



