42 AMICULA. 



(which are not divided into pleura and lateral areas) being micro- 

 scopically densely punctate. Anterior valve (figs. 3, 4) densely 

 punctate and having a few feeble radii. Posterior valve (figs. 8-11) 

 small. 



Interior white. Sutural plates enormously produced ; the sinus 

 very deep, squared and notched at the sides, exposing a projecting 

 lobe of the extremely porous outer layer. Anterior valve having 7 

 or 8, central 1 slit, the insertion-plates extremely long, grooved out- 

 side from the short slits to the eaves. Posterior border of the black 

 tegmentum broadly reflexed inward. Posterior valve (figs. 8-11) 

 elevated, vertical behind, with a broad median notch or sinus and a 

 variable number (1-4) of small slits on each side. 



Girdle leathery, smooth, black. 



Length 60-75, breadth 32-40 mill.' 



Length 50, breadth 20 mill. 



Kamchatka; Aleutian Is.; on the north side of the peninsula of 

 Alaska to Port Hotter, on the south side east to Cook's Inlet and 

 south to Catalina Island, California ; low water (chiefly) to 20 fms. 



Chiton tunicatus WOOD, Gen. Conch., p. 11, t. 2, f. 1 (1815) ; Ind. 

 Test., Chiton, t. 1, f. 10 (1828). SOWERBY, in Beechey's Voy., Zool. 

 p. ]5, t. 61, f. 15. REEVE, Conch. Icon., f. 61. Chiton (Phceno- 

 chiton, Hamachiton, PLatysemus) tunicatus MIDD., Mai. Ross, i, p. 

 98, t. 10, f. 1, 2.Katharina tunieata GRAY, P. Z. S. 1847, p. 69 ; 

 Guide Syst. Dist., p. 185. H. & A. AD., Genera Rec. Moll, i, 

 p. 479 ; iii, t. 54, f. 8. CPR., Suppl. Rep. Brit. Asso. 1863, p. 648. 

 DALL, Proc. U. S. Nat. Mus. 1878, p. 3l3.Katharina dougla- 

 sice .GRAY, P. Z. S. 1847, p. 69. 



" This unmistakeable shell, characterized when fresh by its broad, 

 shining black girdle and almost covered valves, is eaten raw by the 

 natives of the northwest coast, and is said to act as an aphrodisiac" 

 (Dall). The K. douglasice of Gray is founded upon a specimen 

 dried with the girdle flatter and wider. It has no specific or varietal 

 characters. The contour of the exposed portion of the valves, and 

 the number of slits in the tail-valve, vary considerably. The soft 

 parts are of a salmon color in the Northern specimens. 



Genus AMICULA Gray, 1847. 



Amicula GRAY, P. Z. S. 1847, pp. 66, 69, 169 ; Guide, p. 187 (and 

 earlier in Syn. contents Brit. Mus. 42d. edit., 1840, pp. 127, 153, 



