ACM^A. 17 



A. PELTA Eschscholtz. PL 8, figs. 86-95. 



Shell oval, conical, apex a little in front of the middle. Surface 

 having rather coarse low ribs. Dark border of the inside very narrow, 

 or reduced to a series of dark scallops. 



Aleutian Is. an$ south coast of Alaska to the Santa Barbara Islands, 

 California. 



A. pelta ESCH., Zool. Atl. pt. v, p. 19. CARPENTER, Amer. 

 Journ. Conch, ii, p. 336. DALL, Proc. U. S. Nat. Mus. 1878, p. 

 338. Patella fimbriata OLD., U. S. Expl. Exped. atlas, f. 445. 

 P. leucophcea (Nutt.) RVE., Conch. Icon. f. 101. P.monticola~N\jTT., 

 mss. ? A. cassis ESCH., Zool. Atl., p. 19, t. 24, f. 3. ? A. pileolus 

 MIDD., Beitr. zu Mai. Ross, ii, p. 38, t. 1, f. 4, teste Cpr. Collisella 

 pelta DALL, Amer. Journ. Conch, vi, p. 246, t. 14, f. 6 (dentition). 

 Tectura cassis MARTENS, Mai. Bl. xix, p. 92, t. 3, f. 9, 10. Patella 

 cinis RVE., Conch. Icon. f. 60a, b, c. A. pelta var. nacelloides DALL., 

 Amer. Journ. Conch, vi, p, 247, t. 17, f. 36. 



Prominent characters of this species are the erect, conical form, 

 rather wide coarse ribs, and the narrow margin of the inside, usually 

 not continuous but composed of scallops or square spots. 



The variations may be classed under two main groups, as follows. 

 Numerous intermediate forms occur. 



(1) Var. PELTA Esch., typical. PI. 8, figs. 90, 91. 



Rather large, solid, strong, with low coarse ribs, almost obsolete, 

 or visible only posteriorly. Central dark spot of the interior rather 

 small or wanting. Grayish-white, with numerous radiating black 

 stripes, often divaricating or broken into a tessellated pattern. 



As the ribs become stronger this passes into 

 Form cassis (Esch.) Martens. PI. 8, figs. 86, 87, 88, 89. 



Solid, strong, having stout radiating ribs about 25-27 in number, 

 those in front narrower or obsolete. Dark spot of the inside small 

 or obscured ; margin with a mere dark line, or a series of scallops 

 between the ends of the ribs. Outside dull, grayish. 



Another form connecting with the typical pelta is figured on pi. 8, 

 figs. 92, 93, 94. It is small, conical, elevated, having much the 

 shape of A. yiitra. The color outside is gray, pink or light purple, 

 painted with few or many black stripes. A dark spot is inside. 

 Ribs obsolete. This is common at Olympia, Washington, growing 

 on Mytilus. See Hemphill, Proc. A. N. S. Phila., 1881, p. 88. 

 2 



