ACM^A. 13 



the characteristic dark brown stain of patina in the visceral area. 

 The exterior is covered with fine, regularly radiating, close, equal, 

 thread-like riblets, which pass from apex to margin without bifur- 

 cation, imbrication or asperities of any kind. These riblets will 

 serve to distinguish it from any of the other limpets of the coast ; 

 otherwise it approaches very close to some varieties of scabra and 

 can be traced right into some varieties of patina. {Dall.) 



This variety was described from^Monterey, Cal. ; it has also been 

 found on Vancouver Id. 



A. DALLIANA Pilsbry. PI. 7, figs. 57, 58, 59, 60. 



Shell large, oblong, depressed, rather thin. Apex low, curving 

 forward; length of front slope contained about 3? times in the 

 length of the shell ; posterior slope gently convex. Surface covered 

 with close, slightly unequal radiating riblets, each rendered rasp-like 

 by very close, regular and erect delicate lamellse ; interstices narrow, 

 having growth-striae but no lamellse. 



The color is chestnut-brown, becoming dark umber in places, 

 having short streaks and spots of white, forming a sparse tessellation. 

 Inside light blue, with a small brown spot at the cavity of apex, 

 and showing the color-pattern of the outside faintly through. Bor- 

 der wide, deep brown with white spots. 



Length 46, breadth 32, alt. 6i mill. 



Angel Island, Porto Refugio, Gulf of California. 



This is one of the finest American Acmceas. The oblong, some- 

 what parallel-sided and depressed contour, thin texture, and the 

 beautifully sharp and regular lile-like sculpture of the low, close 

 riblets, are its prominent features. It is allied to A. scabra, but the 

 enormous number of specimens of that species wnich I have exam- 

 ined in the Philadelphia and Washington collections, furnish no 

 forms leading toward the Dalliana. The species is named in honor 

 of Dr. \Vm. H. Dall, who outlined the classification of the Acmse- 

 idse in essentially its modern form, twenty years ago. 



A. SCABRA Reeve. PI. 3, figs. 38-49. 



Shell thin, rounded-oval, depressed ; apex situated between the 

 center and the anterior third ; surface sculptured with close, fine, 

 minutely scaly riblets, of which larger ones are placed at regular 

 intervals. Color light yellow 7 , indistinctly spotted (rarely striped in 

 divaricating pattern) with brown. 



