252 Bulletin Vanderbilt Marine Museum, Vol. VI 



A second character, described in detail by Dr. Mortensen 

 (1904) , is to be found in the blades of the tridentate pedicellariae, 

 which are widest near the center. 



Colour : Very black in adults. For description of variations, 

 see Clark (1912 and 1921). 



References: Echinus diadema, Linne^ Syst. Nat., e. X, 1758, 

 p. 664. 



Echinothrix turcarum, Agassiz, A., Mem. Mus. Comp. ZooL, 

 VII, 1873, pi. 3-a, fig. 3.— Mortensen, Th., K. Danske Vid- 

 ensk. Selsk. Skrifter, 7R, Nat-Math. Afd. I, 1904, p. 31. 



Echinothrix diadema, LovEN, S., Bihang, K. Svensk. Vet. Akad. 

 Handl. Bd. XIII, afd. 4, No. 5, 1887, p. 137.— Agassiz, A., 

 and Clark, H. L., Mem. Mus. Comp. Zool., vol. XXXIV, 1908, 

 no. 2, p. 16. — Clark, H. L., Carnegie Inst., Washington, 

 Publ. 214, 1921, p. 147. 



Echinothrix calamaris (Pallas) 



Plates 85 and 86 



Type: Pallas' type, which Peters (1853) selected as the 

 genotype of Echinothrix, was taken at Amboina, and is deposited 

 in the Leyden Museum. 



Distribution : E. calamaris is also a widely distributed mem- 

 ber of the Indo-Pacific littoral fauna, having about the same dis- 

 tribution as its congener, E. diadema. 



Material examined : One large specimen Pago-Pago, Samoa, 

 September 2, 1931. 



Discussion : This specimen has a height diameter of 40 mm., 

 width diameter of 82 mm., and length diameter of 85 mm. The 

 primaries are alternately banded transversely with black and 

 white, while the ambulacral primaries are partly banded with 

 greenish yellow. 



The diagnostic features of E. calamaris (Pallas) are to be 

 found in the primary spines of the mid-region, which are of more 

 fragile structure than those of E. diadema, having the diameter 

 of the central cavity decidedly more than half of that of the spine ; 

 the external surface is ornamented with small spinules arranged 

 in definite whorls. 



The tridentate pedicellariae have the blades of the valves wid- 

 est at or near the distal apex. 



