230 ACANTHOPLEURA. 



Intense black-green inside. Color, pattern and sculpture are as 

 in young C. piceus Grnel., but it differs in the much smaller, more 

 delicate girdle spicules. (Shuttl.) 



Subgenus AMPHITOMURA Pilsbry, 1893. 



Amphitomura PILS., The Nautilus, Jan., 1893, p. 105. Type Ch. 

 borbonicus Dh. 



Girdle and all valves but the eighth formed as in Maugeria. Tail 

 valve having the insertion-plate very short, with blunt, crenulated 

 edge, and a single shallow oblique slit on each side, and sometimes 

 some uneven serrations in the middle. 



The Mopaloid slits of the tail- valve are very peculiar, but the 

 structure is fore-shadowed in some forms of Maugeria. 



A. BORBONICA Deshayes. PI. 45, figs. 76, 77, 78, 79. 



Shell oblong, rather elevated, solid, roundly arched, dull black 

 with a white stripe on each side of the median black band; rusty 

 blackish and gray when eroded ; girdle black. 



The lateral areas are but slightly raised, and are densely, finely 

 sculptured with close radiating rows of granules ; the sides of the 

 central areas are also granulated adjacent to the lateral areas, but 

 toward the middle this sculpture disappears, leaving only a faint 

 microscopic granulation. End valves radially, densely, granulated, 

 the mucro posterior, rather elevated. 



Interior blue-white, each median valve having a broad black square- 

 ended crescent in front of the callus, the inflexed posterior margin 

 ashy-olive, lateral triangles lead- white. Sinus deep, rounded. 

 Anterior valve having 10, central valves 1, posterior valve 2 slits 

 (figs. 76, 77) ; teeth pectinated, those in the front of the head-valve 

 short. Eaves wide, black, channelled along the teeth. Muscle 

 impressions on sutural plates and end valves deep. 



Girdle fleshy, black, covered with black spinules about 1? millim. 

 long. 



Length 50, breadth 30 mill. ; divergence about 125. 



Mauritius ; Reunion. 



Chiton borbonicus DH., Moll. Reunion, p. 37, t. v, f. 12, 13. C. 

 (Acanthopleura) borbonicus Dh., MARTENS in Mobius' Reise nach 

 Mauritius, p. 300. ? ? Chiton nebulosus WOOD, Index Test, Suppl., 

 t. 1, f. 4. 



