i80 Bulletin Vanderbilt Marine Museum, Vol. VII 



Distribution : This species is widely spread in the tidal zone 

 of the Indo-Pacific from Kosseir, in the Red Sea through the 

 Indian Ocean at Mauritius and Zanzibar and in the tropical 

 Pacific in the Philippines, Torres Straits, Bonin and Marshall 

 Islands, Amboina, Rotti, Sula Besi, Fiji Islands, Samoan Islands, 

 Tahiti, Society Islands, Hawaiian Islands, Cocos Island and Gala- 

 pagos Archipelago. It has been reported from the tropical shores 

 of the Atlantic Ocean at Bahia, Brazil and Surinam. Dr. H. L. 

 Clark questions the correct identity of these South American 

 specimens. 



Material examined: Two smallish specimens, from Apia, 

 Samoa, September 5, 1931, collected by the "Alva." 



Colour : The living animal has the body colour creamy whit- 

 ish, with well scattered spots of reddish brown and five or six 

 well separated longitudinal whitish bands. 



Technical description : The living animal is elongate, sub- 

 cylindrical, with the dorsal surface arched, the ventral surface 

 less so, both ends blunted, the mouth ventrally inclined, small; 

 the tentacular circle is surrounded by an inconspicuous collar 

 bearing small papillae. The tentacles are very small (very re- 

 tracted in the dead specimens), twenty in number. The anus is 

 distal, margined by annular groups, each consisting of four to 

 six short papillae. The ambulacral appendages are represented 

 by irregularly scattered pedicels, those of the two ventral ambu- 

 lacra being larger and more numerous than those of the dorsal 

 surface. The peristome is of medium thickness. The deposits are 

 of two types, "buttons" and tables. The tables consist of an 

 annular disk, quadrate-circular in outline, having a very large 

 central hole and normally, four smaller holes, one placed at the 

 base of each rod of the spire, (some tables exceed this arrange- 

 ment, having as many as six small holes) ; the spire is composed 

 of four upright rods, one transverse bar and a denticulate crown 

 with twenty to thirty-six teeth. The "buttons" are rather regu- 

 larly shaped, oval with the circumference undulating, the surface 

 smooth, the perforations occurring in the wider radius of the 

 button, usually six, sometimes eight. The rods in the pedicels are 

 smooth, dilated at both ends and in the middle and also having 

 several perforations here. The calcareous ring is small, the 

 radialia are nearly as wide as long and are truncate anteriorly 



