258 Bulletin Vanderbilt Marine Micseum, Vol. VI 



The "Alva" specimens measure (in millimeters) : 

 Height Width Length Height Width Length 



The pore pairs at and above the ambitus are arranged in arcs 

 of four, and in some specimens in arcs of five. The genital plates 

 each average four to six secondary tubercles. The primary spines 

 are rather short, their length averaging 0.4 to 0.5 of the width 

 of the test. In colour these spines are quite variable. Of the seven 

 larger Tahitian specimens (alcohol preserved), four specimens 

 have the proximal 0.5 to 0.6 of the primaries deep brownish- 

 purplish, with the remaining distal portion creamy white; two 

 other large specimens have the primaries faded deep greenish 

 proximally and distally, are pinkish-lavender-creamy, while an- 

 other specimen has the primaries entirely cream colour but with 

 a faded lavender tinge proximally. The test of all these specimens 

 is brown or purplish-brown. 



References : Echinus mathaei, de Blainville, H. M., Diet. Sci. 

 Nat., t. XXXVn, 1825, p. 94. 



Echinometra mathaei, de Blainville, H. M., op. cit., t. XXXL, 

 1830, p. 206.— Clark, H. L., Pub. 214, Carnegie Inst. Wash- 

 ington, Dept. Marine Biol. Papers, 1921, p. 151 ; Catal. Re- 

 cent Sea-urchins, B. M. N. H., 1925, p. 143. 



Echinometra lucunter, Agassiz, A., Mem. Mus. Comp. Zool., vol. 

 VIII, pt. Ill, 1873, pi. 4-b, fig. 4. 



Genus: HETEROCENTROTUS Brandt 

 Heterocentrotus trigonarius (Lamarck) 



Plates 95 and 96 



Type : Lamarck's type specimen was without reliable locality, 

 his citation being "Habite . . . la Mediterranee? Mon cabinet." 

 This was later deposited in the Paris Museum. 



