Order CIDAROIDEA 



Family CIDARIDAE 



Genus HISTOCIDARIS Mortensen 



HISTOCIDARIS MAGNIFICA, new species 



Plates 48-49; 76, figs. 1-3 



Locality. — Station 5547; near Jolo (Sulu) ; Tulayan Island (E.) 

 bearing S. 38° E., 9.5 miles distant (lat. 6° 09' 20" N., long. 121° 13' 

 40" E); 283 meters; bottom temperature 13.50° C; fine sand; Sep- 

 tember 15, 1909 (1 specimen, the type, Cat. No. E. 5547, U.S.N.M.). 



Measurements 



Description. — The shape of the test is almost perfectly globular, 

 though it is uncertain whether or not there is a slight flattening of 

 the oral side, as it did not seem desirable to remove the perfectly 

 preserved spines of the oral side in order to ascertain this, which for 

 the description of the species is a rather unimportant detail. 



The ambulacra are fairly broad, 10 mm. or 28.6 per cent of the 

 interambulacra, which latter measure 35 mm. in breadth at the 

 ambitus. The interporiferous zone is 3.3 mm. broad, thus almost 

 exactly as broad as each poriferous zone. Both pores are unusually 

 broad, separated only by a very narrow and scarcely projecting wall. 

 The plates are very low, the pairs of pores therefore lying very closely 

 one above another. Also the marginal series of tubercles is very 

 crowded, the tubercles being nearly in contact, though rather small. 

 (Fig. 1.) The marginal series is very regular. Inside the marginal series 

 t/nere is at the ambitus and farther downward a fairly regular series 

 of smaller tubercles on each side ; above the ambitus the inner series 

 become irregularly alternating, totally disappearing in the upper part, 

 where the interporiferous zone gradually becomes much narrower. 



The primary tubercles of the interambulacra are strongly crenulate, 

 the areoles nearly confluent, except the three upper ones, the following 



245 



