OF CONCHOLOGY. 335 



to me that lie never took it, nor have I ever seen black limpets 

 of that size in any authentic South American collection. Small- 

 er shells of the same aspect are, however, undoubtedly South 

 American, being described by D'Orbigny under the name of A. 

 scutum, as of Eschscholtz, and occurring, in tolerable abund- 

 ance, in the United States Exploring Expedition Chilian and 

 Patagonian collections. These go through the usual Northern 

 changes of form from scutoid to patinoid ; are more or less 

 spotted ; and vary in sculpture. Normally they have closer 

 stria?, as in A. testudinalis ; but fresh specimens are often 

 nearly smooth, and in others (especially the flatter specimens) 

 the striae become further apart, and would not be recognized 

 as distinct from A. patina in a mixed collection. It will save 

 confusion to retain D'Orbigny's name, as A. scutum, D'Orb., for 

 the South Americans ; and to distinguish the Northern black 

 varieties of patina as Gumingii, that being the name given to 

 the most characteristic forms. The A. cantharus, Rve., (Cape 

 of Good Hope, Archer, certissime : " Guacomayo," Mus. Smithso - 

 nian,) can scarcely be distinguished from the flattened South 

 Americans. 



The A. mamillata of Nuttall is the young state of Gum- 

 ingii, somewhat conical and arched ; but the A. mamillata of 

 Eschscholtz is a var.of Scurria mitra, testibus Philippi, Midden- 

 dorff; while the shells now called mamillata in Mus. Cuming, 

 as of Eve., are the black var. {limatula) of A. scabra, Nutt. 

 The shells quoted by Dr. Gould under pintadina, p. 352, 

 from the Boston Cab. A. N. S., are also probably A. scabra, 

 Nutt., which is always known from A. patina by the rough 

 striation. 



A very pretty modification of the Gumingii type is verricu- 

 lata, Eeeve, of which fenestrata, Nutt., is the young. In this, 

 the color-pattern is in a minute network, as in some vars. of 

 persona. In A. cinis, Reeve, the same pattern is changing into 

 the streaked varieties. 



A. patina, var. d., is internally almost always dark in the 

 spectrum, with white sides. But sometimes there are concen- 

 tric zones of dark, alternating with the white, in which state it 

 is the "A. cribraria," Gld., ms., a very worn specimen of which 

 was "purchased at the Sandwich Islands" by the omnivorous 

 naturalists of the United States Exploring Expedition. Some- 

 times the spectrum is well defined, nearly black ; and the 

 sides are dark brown. The intermediate forms and shades 

 between the vars. Cumingii and pintadina are very common. 

 Sometimes the marginal edge grows light, with a dark belt 

 inside ; or the dark becomes more or less spotted. The out- 

 side almost always displays more or less of spots, generally 

 in very small pattern. 



