TONICIA. 205 



areas ; the growth wrinkles, which on the lateral areas are close and 

 prominent, are weaker on the central areas, the posterior part of 

 which appear sculptureless. The umbo seems to be produced back- 

 ward [beaked] in young shells, but in this specimen it is so upon the 

 2d valve only. The dorsal ridge is bluntly angular. The head 

 valve is long compared with its breadth, the length of the front 

 slope equalling that of each of the posterior margins ; it shows weak 

 concentric sculpturing of strise. The tail-valve is small and narrow, 

 not much more than two-thirds as broad as the head valve, and also 

 notably shorter ; its forward area is not shining ; the posterior 

 segment is shining and sculptured like the head valve. 



The lateral areas and the outer anterior parts of the central areas 

 are yellowish-red with red marbling. The central area shows on 

 its middle part, a group of beautiful chocolate-brown and violet- 

 white strise, radially diverging from the umbo. On the anterior 

 median valves are seen also a few clear brown streaks on the outer 

 part of the central areas. 



The single specimen before me is fastened on pasteboard, and 

 measures 13'5 by 6 mill.; the broadest valve is 5 mill., so that the 

 girdle is but *5 mill., wide. The third median valve of this specimen 

 is abnormal in being pure white. 



South Georgia. 



Chiton zschaui PFFR. in Moll. Siid-Georgien, Jahrb. Hamb. 

 Wissensch. Anstalten iii, p. 105, t. 3, f. 2 (1886.) 



This is placed in Tonicia with much doubt, for the presence of 

 eyes is not noted in Pfeffer's description, above. 



T. TEHUELCHUS d'Obigny. PI. 40, figs. 13, 14, 15. 



Shell oblong, elevated, strongly carinated ; brown with two white 

 longitudinal zones ; head-valve and lateral areas radially sulcate- 

 bifurcate ; central areas longitudinally punctate-silicate. 



Length 27 mill. (Orb.) 



Bay of San Bias, Patagonia. 



Chiton tehuelchus ORB., Voy. dans 1'Amer. Merid., p. 488, t. 65, 

 f. 7-13. 



The sculpture reminds one of Chcetopleura fulva Wood. The 

 generic position is not certain. 



2. West Indian species. 

 T. SCHRAMMI Shuttleworth. PL 43, figs. 54, 55, 56. 



Shell oblong, moderately elevated, roundly angular. Surface 

 polished. Ground-color buff, mottled, speckled or sometimes suffused 



