154 Bvlletin Vanderbilt Marine Museum, Vol. VII 



based on extensive material, have each concluded that these two 

 are distinct but closely related species. M. Koehler points out the 

 several secondary characters by which erinaceits may be distin- 

 guished. Mr. Clark records observations made of the living ani- 

 mals on the reefs in Torres Straits, where scolopendrina was very 

 abundant. 



Ophiocoma molaris Lyman and Ophiocoma lubrica Koehler 

 are also placed as synonyms of scolopendrina. 



A typical "Alva" specimen, taken at Samoa, has the disk cir- 

 cular, with a diameter of 20.5 millimeters and the arms measuring 

 from 60 to 65 millimeters long. The abactinal surface of the disk 

 and the interbrachial regions of the actinal surface are covered 

 with coarse, rounded, blackish granules which almost touch one 

 another but do not overlap, there being 12 to 15 granules per 

 square millimeter. No radial shields are visible. The mouth shield 

 is small, somewhat shield-shape, being widest across the outer 

 third of the shield, with the outer margin beyond this point 

 rounded and the inner lateral borders slightly convergent to the 

 broadly truncated inner margin. The side mouth shields are tri- 

 angular, fitting close to the inner lateral margins of the central 

 shield and not meeting inwardly. There are five mouth papillae 

 on each side, the outer two of these being very wide, bluntly trun- 

 cated distally ; these are followed by three, each one-half so wide, 

 blunt, distally small teeth, on either side of the similar but smaller, 

 subacute cluster of three apical teeth. The teeth are strong with 

 widely truncate, blunt tips. 



The arms are comparatively wide and stout. The under arm 

 plates are small, broad-axe shape, with the inner margin narrowed, 

 nearly straight, usually concealed by the overlapping adjacent 

 plate; the distal margin is widely convex; the side margins are 

 concave for the greater portion, beside the tentacle pore and be- 

 yond this are directed obliquely inward the proximal margin. 



The tentacle scale is wide, oval. The side arm plates each bear 

 four spines. These spines increase in size appreciably from ven- 

 tral to dorsal of the series. Each spine is quite stout, blunt tipped, 

 being definitely thicker throughout the proximal half and tapered 

 slightly on the distal half. The dorsal arm plates are small, wider 

 than long, being 1 millimeter long and 2 millimeters greatest 

 width, with the inner margin short, being only about one-fifth of 

 total arm width, straight, the lateral margins are oblique and the 



