Boone, Echinodermata, Cruises of "Ara" and "Alva" 181 



with a small, obtuse incision, the posterior margins are slightly 

 excavate. The interradial pieces are much smaller than the radial ; 

 anteriorly each has one tooth, the posterior margin is conspicu- 

 ously excavated. There are two Polian vesicles present in one 

 specimen and a double madreporic canal. Cuvierian organs are 

 absent. 



References: Sporadipus (Alcolpos) maculatus, Brandt, J, F., 

 Prodom. descript. anim., 1835, p. 46. — Lampert, K., Die 

 Seewalzen, 1885, p. 73. 



Holothuria arenicola, Semper, C, Reisen im Arch, der Philippinen 

 Wissensch. Resul. I, Holothurien, 1867, p. 81, pi. 20, pi. 30, 

 fig. B, pi. 35, fig. 4.— Theel, H., Rept. Voy. H. M. S. "Chal- 

 lenger" Zool., Holothuroidea, pt. II, 1886, vol. XIV, p. 222.— 

 Fisher, W. K., Proc. U. S. Nat. Mus., vol. XXXII, 1907, p. 662, 

 pi. 68, fig. 95.— Clark, H. L., Publ., 214 Carnegie Inst., 

 Washington, Dept. Marine Biol. Papers, vol. X, 1921, p. 173. 



Holothuria macuhita, Sluiter, C, Ph., Siboga-Expeditie Holo- 

 thurien, Monogr. LXIV, Livr. 1, 1901, p. 9. 



Genus: ACTINOPYGA Bronn 

 Actinopj'ga mauritiana (Quoy and Gaimai'd) 



•f 



Distribution : This species is very abundant and widely dis- 

 tributed in the tidal zone of the Indo-Pacific, having been reliably 

 reported from the Red Sea southward to Mozambique, northward 

 to the Riu Kiu Islands, Japan, eastward to the Hawaiian Islands 

 in the north central Pacific and to the Marquesas Islands, Society 

 Islands and Paumotu Archipelago in the south. 



Material examined: Nine large and two small specimens 

 from Venus Point Reef, Tahiti, Society Islands, August 15, 1931. 



These "Alva" specimens appear to be the second record of this 

 species from the Society Islands. 



Colour: Dr. W. K. Fisher records that many specimens of 

 Actinopyga mauritiana (Q. and G.) which he examined in the 

 Hawaiian Islands vary considerably in shades of brown and the 

 amount of white present. The usual form is coloured a rich raw 



