248 



BULLETIN 100, UNITED STATES NATIONAL, MUSEUM 



The color of test and secondary spines is dark brownish the pri- 

 maries whitish-brownish with the collar somewhat darker. 



Remarks. — This splendid large species is very markedly distinct 

 from all the other species of this genus hitherto known; it does not 

 seem very closely related to any of them. 



HISTOCIDARIS ACUTISPINA, new species 



Plate 50, figs. 1, 2; plate 52, fig. 2; plate 77, fig. 4 



Localities — Station 5429, near eastern Palawan; Fondeado Island 

 (SE.) bearing N. 18° E., 15 miles distant (lat. 9° 41' 30" N., long. 

 118° 50' 22" E.); 1,401 meters; green mud; April 5, 1909 (a few 

 primary spines, Cat. No. E. 1285, U.S.N.M.). 



Station 5495, between Leyte and Mindanao; Diuata Point (N.) 

 bearing S. 76° E., 9.4 miles distant (lat. 9° 06' 30" N., long. 125° 

 00' 20" E.) ; 1,785 meters; bottom temperature 11.28° C; gray mud; 

 August 2, 1909 (1 specimen, the type, Cat. No. E. 1275, U.S.N.M.). 



Measurements 



Description. — In shape the test is rather low, with the sides gently" 

 curving. 



The ambulacra are 3 mm. broad, the interporiferous zone being 

 1.2 mm. broad, thus slightly broader than each poriferous zone. 



* 



Fig. 4— Part of ambulacrum or Histocidaris acutispina, new species (a) and 

 of Histocidaris, species (6) X 12 



The marginal series of tubercules is regular, the tubercules being 

 small and relatively distant; within the marginal series there is only 

 here and there a small tubercule, the zone being thus almost wholly 

 naked; it is not sunken. The pores are subequal in size, the inner 

 one only indistinctly the larger. The wall between the pores is very 

 little prominent. (Fig. 4a.) 



