332 AMERICAN JOURNAL 



ON THE ACM-EID^ OP THE VANCOUVER AND 

 CALIFORNIAN PROVINCE. 



BY PHILIP P. CARPENTER, B.A., PH.D. 



Genus ACM^^A, Esch. 



The ordinary Acmasids of the Californian and Northern 

 shores divide themselves into the following principal groups: — 



1. Patina.— 'Normal shape; often smooth, but, when well 

 developed, with very fine, sharp, distant stripe; black, or tes- 

 selated with olive-brown ; margin moderate. 



2. Pelia. — Similar shape; not striated ; with faint swelling 

 ribs, sometimes nearly obsolete ; margin narrow. 



3. Persona. — Apex pointed forwards; generally with obtuse 

 ribs, and dome-shaped; sometimes spreading, with faint rib- 

 lets. 



4. Spectrum.. — Apex somewhat anterior; not dome-shaped; 

 with very strong, close, rounded ribs. 



5. Scahra. — Shape of patina, with close, nodulous stria3. 



There are numerous intermediate forms, even between these 

 clearly -defined groups; and in each, special forms are devel- 

 oped, which have been regarded as distinct species. Until 

 the animals of these shall have been proved to present clear 

 marks of separation, they must be regarded as simply the ac- 

 cidents of growth. 



ACM^A PATINA, Esch. 



(For synonymy, vide Maz. Cat. and Br. Assoc. Reports, in locis.) 



This species having been first described from dwarfed 

 Northern specimens, it could only be recognized, along with 

 the other Sitcha limpets, by the judgments of Philippi, Mid- 

 dendorflf, and others, who had seen the shells; and by the use- 

 ful axiom, that when authors describe the species of a partic- 

 ular locality, they mean the shells known to inhabit that lo- 



