ISCHNOCHITON. 133 



figure and description given by Reeve. 



I. PUSIO Sowerby. 



Shell oval, smooth ; olivaceous, ornamented with numerous green 

 dots; front and side margins of the valves rugulose. Marginal 

 ligament scaly. Length 12, breadth 7? mill. (Sowb.) 



Valparaiso, on Amphidesma solidum, 30-50 fms. ; sand bottom. 



Chiton pusio SOWERBY, P. Z. S. 1832, p. 105. 

 I. DALLII Haddon. PI. 25, fig. 1-10. 



Shell evenly covered with closely set minute low tubercles, which 

 give it a granular appearance ; with straight-sides meeting at an angle 

 of 110. Anterior valve closely granular, with twenty-six short radial 

 rows of tubercles, each row consisting of four or five tubercles, which 

 diminish in size from the periphery towards the apex ; the posterior 

 row is the broadest, and is partially bifid. 



Intermediate valves. Central area: jugum coarsely granular; 

 pleura with about 12 or 13 distinct horizontal ridges; lateral areas 

 granular, with three main radiating rows of tubercles, the anterior 

 and posterior often partially double. Posterior valve remarkably 

 flat, coarsely granular, with nineteen rows of three tubercles each, of 

 which the outermost is the largest ; umbo scarcely, if at all, raised 

 above the surface ; anterior border coarsely granular, with the 

 granules passing into oblique ridges on the pleura. 



Girdle medium breadth, upper surface with smooth imbricating 

 scales in oblique rows, about seven or eight in a row, those nearest 

 the shell being the smallest. Color greyish -white. 



Length 11, breadth 6, height about 3 mill. 



Gills extending to about three-quarters the length of the foot, 

 diverging posteriorly and hidden by a slight swelling of the longitu- 

 dinal band on the under surface of the girdle ; about twenty-one in 

 number, largest about the fifth from the posterior end, and gradually 

 diminishing in size anteriorly. (Haddon.) 



Lat. 51 27' 30" S., long. 74 3' W., 400 fms. blue mud. 



Lepidopleurus dallii HADDON, Challenger Polyplac., p. 19, t. 1, f. 

 6, t. 3, f. 6a-6i. 



I have associated this species with the name of my friend Mr. W. 

 H. Dall, of the Smithsonian Institution, Washington, U. S. A. 

 (Haddon.) 



