ASTEOPYGA RADIATA. 123 



(1904) suggests that they seem to be near Choetodiaderna ; while this is 

 true in certain respects, the hollow spines show they are no nearer to that 

 genus than to Astro pyga. 



ASTROPYGA. 



Gray, 1825. Ann. Phil. p. 4. 

 Type-species, Cidaris radiata Ijeske, 1778. Add. Klein, p. 116. 



Since Agassiz in 1846 named Astropi/ga piilvinata, no valid species has been 

 added to this genus, so that we find it necessary to recognize only two. Of 

 these, radiata (Leske) occurs throughout the Indo-Pacific region from Zanzi- 

 bar to Hawaii, while jndvinata Agass. is known only from the West Coast of 

 Mexico and Central America. The tuberculation of the actinal side of the 

 test will always distinguish specimens of these two species, but the color is 

 also a useful character. Both are distinctly littoral. 



Columns of primary tubercles on actinal surface parallel with ambulacra, so 

 that outermost column (next to ambulacrum) at ambitus, extends to peri- 

 stome, though the tubercles may become much smaller there; general colora- 

 tion more or less red or reddish radiata. 



Columns of primary tubercles on actinal surface parallel with midline of inter- 

 ambulacrum, so that outermost 2 columns on each side do not reach peristome ; 

 general coloration more or less greenish ; no red pulvinata. 



Astropyga radiata Gray. 



Cidaria radiata Leske, 1778. Add. Klein, p. 116. 

 Astropyga radiata Gray, 1825. Ann. Phil., X, p. 4. 



The "Albatross" took a single, young specimen (26 mm. in diameter) of 

 this species at the following station : 



Station 3875. Auau Channel, between Maui and Lanai. Bott. temp. 

 70.8°. 34-65 fathoms. Fne. gy. s. One specimen. 



Ch^todiadema. 



Mortensen, 1903. Vid. Med. Nat. For. Kjobenhavn, p. 1. 

 Type-species, Chmtodiadema granulatum Mortensen, 1903. Vid. Med. Nat. For. Kjoben- 

 havn, p. 1. 



Although closely allied to Astropyga, this genus is easily distinguished 

 by the much flatter test and smaller actinostome, as well as by the more im- 

 portant characters of the ambulacra and actinal surface, already mentioned. 



