16 ACM^A. 



4-6. — A. digitalis Esch., I. c, t. 23, f. 7, 8. — P. wnhonata Nuttall, 

 in RvE., Conch. Icon. f. 107. — P. oregona Nutt., /. c, f. 112. — L. 

 textilis Gould, Expl. Exped. Sh. t. 29. f. 456.— ColliseUa per- 

 sona Dall, Amer. Journ. Conch, vi, p. 250, t. 14, f. 8 (dentition). — 

 L. scabra Gld. (in part), Expl. Exped. Sh., f. 456b. — A. radiata 

 Esch., Zool. Ail. p. 20. — Techira persona Martens, Mai. Bl. xix, 

 p. 95, t. 3, f. 5, 6. 



An excessively variable species, ranging from about 30° to 50° 

 N. lat. 



The typical persona is rather a smooth shell, corresponding to 

 figs. 51,52, of plate 3. 



Two main races may be distinguished. The minor modifications 

 of each are numberless. 



Var. DIGITALIS Esch. PI. 2, figs. 29, 30, 31 ; pi. 3, figs. 53, 54, 55, 56. 

 This is the most usual form found north of San Francisco Bay. 

 It is dull, lusterless, whitish, with stripes and zigzags of blackish- 

 brown. The apex is usually decidedly anterior and elevated ; the 

 front ribs are obsolete, the posterior ribs strong, rounded, often 

 uneven. Inside margin conspicuously tessellated ; central area 

 generalh" dark and rather narrow. This is the oregona of authors, 

 and probably radiata of Eschscholtz. It resembles the striped vari- 

 ety of the Chilian A. ceciliana so closely that it would be absolutely 

 impossible to separate a mixed lot. 



Var. UMBONATA Nuttall. PI. 2, figs. 25, 26, 27, 28. 



The prevalent form southward of San Francisco is an oval shell 

 with rather spreading sides, the ribs narrow, interspaces wide and 

 flat. Color dark olive to blackish, closely flecked with fine white 

 dots, and usually having coarse white dashes also. 



This variety becomes at times wholly free from ribs. 



Another variety, typically equally distinct, but nameless, is found 

 rom San Francisco to San Diego. It is a small shell resembling 

 somewhat ^. joa^ma. There are no riblets. The surface is luster- 

 less, white, with numerous, rather narrow, radiating brown stripes, 

 often broken or abruptly divaricating. Inside generally without a 

 central dark area. Gould's figures of the synonymous L. scabra are 

 copied on pi, 29, figs. 47, 48, 49. 



