OP CONCHOLOGY. 341 



lirulis quibiisdam majorilus, valde nodosis ; intus albida, ni- 

 tidit; limbo lato nigro, sea rarius tesselato ; spectro soepivis 

 fusco maculate. 



It is probably the Acmasa jJciti'na of the Mazatlan Catalogue, 

 sp. 265, but the specimens were too much worn outside to de- 

 cide with confidence. 



Hahitat. — San Pedro, Cooper, Palmer; Sta. Cruz, Rowell; 

 Monterey, Rich; Mazatlan, Reigen. 



Ordinary collections ot limpets from the coast may generally 

 be grou]ied under the above five species ; the three first only 

 being Northern. A few individuals, however, are (rarely) 

 met with, which must continue to perplex malacologists till 

 more specimens have been compared, and their animals ex- 

 amined. They belong to two distinct forms. The first is 



AcM^A A SMI, Middendorf. 



This is easily recognized by its small size, very conical 

 shape, uniform dark color, and great solidity. It is generally 

 rounder than Nacella incessa; and the latter has a horny aspect, 

 and is moderately thin. Among all the myriads of limpets 

 which I have handled, I have never seen more than about 6 

 specimens of A. Asmi. I am inclined to regard it as a stunted 

 variety of one of the other species, probably pelta though it 

 may be a cross between that species and^a^ma, var. Cumingii. 

 This view is confirmed by one of Dr. Cooper's specimens, in 

 which the adult shell is a normal pelta, while the young por- 

 tion would have made an excellent J-sm^', if detached from the 

 rest. 



AcM^A (?var.) rosacea, Carpenter. 

 Brit. Assoc. Rep. 1863, p. 650, no 248, 

 =A. pileolus, Mus. Gum. : fnon Middendorf. 



A. t. parva, conica, tenui, liBvi; t. jun. pallide rosacea, ele- 

 gantissime maculis albis et fuscis subradiatimsparsis; t. adulta 

 strigis fusco-rosaceis et albidis picta; apice elevato, parum 

 antico; intus rosacea. Long '2, lat. '16, alt. '08 poll. 



Habitat. — S. Diego, Monterey, Cooper. 



Specimens of this species are named "pileolus^ Midd.," in 

 Mus. Cuming, and are said to have been received by Mr. 

 Damon from Middendorff himself. But there surely must be 

 some mistake, as the following is the author's diagnosis, in his 



