POLYPLACOPHORA. 113 



CHITON CASTANEUS (Couthouy) Old. PI. 14, fig. 5. 



Animal with the under side of the margin pale brick-red ; foot 

 narrow oval, dull olive color : head small, and laterally compressed ; 

 branchiae pale ochreous-red, extending from the anterior margin of 

 the foot to the rectum, leaflets conical, compressed, tapering to a fine 

 point. ( Old.} 



Shell minute, elongated-oval, slightly narrowed anteriorly, sub- 

 carinate, valves obtusely beaked, without distinct lateral areas, but 

 marked throughout with coarse sublaminate ridges of increment, and 

 covered with minute punctures arranged in quincunx ; posterior 

 valve with an obtuse umbo. Color externally deep chestnut, 

 internally dull red. Margin narrow, thin, coriaceous, finely pubes- 

 cent, having at the inner margin twenty-six fascicles of short, rigid, 

 shining white setae, looking like minute polished tubercles. (Old.) 



Length 1}, breadth 22 mill. 



Orange Harbor, Patagonia, on old shells and in tide pools. (U. 

 S. Expl. Exped.). 



Chiton castaneus COUTH. MS., GOULD, U. S. Expl. Exped. Moll., 

 p. 326, f. 411, a-c (not Ch. castaneus Wood, nor Q. & G.). Acan- 

 thochiton couthouyi ROCHKBR., Polyplac. Cap Horn, p. 133. 



A small but very distinct species, most of the specimens were con- 

 siderably eroded showing that they had come to maturity. (Gld.y 



The generic position of this form is problematical. It cannot be 

 an Acantlwehites. Rochebrune gives no information except that it 

 was collected in the Strait of Magellan by the French expedition of 

 1882-83 to Cape Horn. 



CHITON BRODERIPI Potiez & Michaud. It is oval, rotund, thick, 

 of a brown or dirty white color ; the dorsal line is smooth and black- 

 ish ; the anterior valve is marked with a white spot at the summit, 

 and the posterior is swollen and retuse within ; these two valves and 

 the intermediates valves are grooved, striated and somewhat gran- 

 ulated at the lateral areas from base to summit. The margin is 

 thick and leathery. Length 40, width 30 mill. (P. & M., Galerie 

 des Moll, du Mus. de Douai, i, p. 533, 1838). 



Sea of Chili.. 



TONICIA GAUDICHAUDI Rochebrune. Shell ovate, subcarinated, . 

 shistaceous-tawny, pictured with small violaceous spots. Anterior 

 valve and posterior part of posterior valve concentrically lineated;. 

 8 



