250 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



the base. Those of the ambulacra are simply setaceous, erect, almost 

 as long as those around the primary spines. 



The pedicellariae are up to about 3 mm. in length of head, with 

 slender, elongate valves (pi. 77, fig. 4); the blade is filled with a close 

 mesh work, with more or less distinct longitudinal crests; there is no 

 depression above the apophysis. 



The spicules of the tube feet are of the usual type. 



The color of the test and secondary spines is light yellowish brown; 

 the primaries are white, with the collar faintly yellowish brown like 

 the test. 



Remarks. — The highly characteristic primary spines make this spe- 

 cies easily distinguishable from H. elegans, to which otherwise it is 

 apparently the nearest related. Probably also the secondary spines 

 and the apical system will be found to offer good distinguishing 

 characters when once the adult form comes to hand, while the pedi- 

 cellariae are not very different from some forms of those of II elegans. 



The spines of a specimen dredged off Somaliland by the German 

 Deep-sea Expedition ' ( Valdivia), referred to II. elegans by Doderlein, 

 to some degree resemble those of the present species; still this speci- 

 men hardly belongs here. It is noteworthy especially that the 

 spinules on the spines are distinctly arranged in longitudinal series > 

 as is not the case in the present species. Doderlein gives no informa- 

 tion concerning the details of the structure of these spines. 



HISTOCIDARIS ELEGANS (A. Agassiz) 



Plate 52, fig. 1; plate 77, figs. 1-3 



Porocidaris elegans A. Agassiz, Challenger Reports, Zoology, vol. 3, pt. 9, 

 Echinoidea, 1881, p. 40, pi. 3. — H. L. Clark, Bull. Mus. Comp. Zool., 

 vol. 51, No. 7, 1907, p. 227. 



Hislocidaris elegans Th. Mortensen, The Danish Ingolf-Exped., vol. 4, pt. 

 1, Echinoidea, 1903, pp. 21, 30, 173.— H. L. Clark, Biol. Results Fish- 

 ing Exper. F. I. S. Endeavour, 1909-1914, vol. 4, pt. 1, 1916, p. 105; 

 Cat. Recent Sea-Urchins Brit. Mus., 1925, p. 37. 



Localities. — Station 5446; eastern coast of Luzon; Atalaya Point, 

 Batag Island, bearing S. 64° E., 5.3 miles distant (lat. 12° 43' 51" 

 N., long. 124° 59' 18" E.) ; 540 meters; green mud; June 3, 1909 (1 

 specimen, Cat. Nos. E. 1307, E. 1308, U.S.N.M.). 



Station 5450; eastern coast of Luzon; East Point, Batan Island, 

 bearing S. 36° E., 9.2 miles distant (lat. 13° 23' 15" N., long. 124° 

 00' 30" E.); 734 meters; bottom temperature 5.72° C; green mad 

 and coral; June 4, 1909 (1 specimen, Cat. No. E. 1274, U.S.N.M.). 



Station 5510; vicinity of northern Mindanao; Camp Overton Light 

 bearing S. 68° E., 9.1 miles distant (lat. 8° 16' 00" N., long. 124° 03' 

 50" E.); 7G1 meters; bottom temperature 11.67° C; gray mud and 

 fine sand; August 7, 1909 (2 specimens, Cat. No. E. 1283, U.S.N. M.). 



1 Ech. Deutsche Tiefsee-Exped., pi. 13, fig. 4. 



