42 AMKll.A. 



(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- 

 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 60-7f), breadth 32-40 mill. 



Length 50, breadth 20 mill. 



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

 Alaska to Port MiJll< r, on the south side east to Cook's Inlet and 

 <?Hth to Catalina Island, California; low water (chiefly) to 20 fm.s. 



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. 1 "), t. (51, f. 15. REEVE, Conch. Icon., f. 61. Chiton (Phceno- 

 chiton, Hamachiton, Piatysemuuf) tunicatus Minn., Mai. Ross, i, p. 

 98, t 10, f. 1, 2. JTaCfcarwM tiuncnta <;KAY, P. Z. S. 1847, p. 69 ; 

 vst. Dist., p. 185. H. <fc A. An., Genera Rec. Moll, i, 

 j>. -17H ; iii. t. 54, f. 8. CPR., Suppl. Rep. Brit. Asso. 1863, p. 648. 

 DALL, Proc. U. S. Nat. M us. 1878, p. 313. Knthnrlna d<.nfjla- 

 sics 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 

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

 ''). The A', 't'tut/latfa 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. 



- i 847, pp. 66, 69, 169 ; Guide, p. 187 (and 

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



