342 PROCEEDINGS OF UNITED STATES, NATIONAL MUSEUM. 



After eliminating some of these, there remained, after careful study, a 

 residue, which do not appear to coincide in character with any described 

 species. They are small, thin, corneal, with a blunt, erect apex marked 

 by a light yellow spot, the rest of the exterior white or faintly yellowish, 

 marked by obsolete lines of growth, smooth, or nearly so, but not pol- 

 ished. Within, fresh specimens are yellowish, whitish, or orange-col- 

 ored, and quite polished. The outside is almost always covered with 

 nullipore. The chief characters are the rounded base, regularly conical 

 and yellow spotted apex, with a thinner shell than young A. mitra. 



Fam. PATELLIDiE. 

 Genus N AC ELLA Schumacher. 



NaceJla (Sclium.) Dall, 1. c. p. 274, 1871. Type N. mytilina Gin. 



Nacella ? rosea. 



Nacclla? rosea Dall, Proc. Cal. Acad. Sci. iv, p. 270, pi. 1, f. 2, Oct. 1872. 



Hah. — Dead on exposed ocean beaches at Kyska Island, Aleutians, 

 and Simeonoff Island, Shumagins. Alive onfuci oil" shore? Forty-five 

 specimens obtained, all dead. 



This exquisite little rose-leaf <>r a shell exactly resembles the type of 

 the genus Nacella in form, and is the only one of the so-called Xaccllccot' 

 the northwest coast which has not been proved to be an Aemaiid. It 

 is only provisionally referred to this family, and may prove, like the 

 others, non patclloid when the animal becomes known. 



In this connection it may be of interest to quote the words of Esch- 

 SCholtz in describing the £enus Acmaia* words which at one time were 

 partially discredited, but which the march of science has proved literally 

 tnie: — ' k Here" (at Sitka) are found u six species of a genus which from 

 its Simple unwound shell would be immediately taken for a Vatella; the 

 Creature, however, closely resembles the Fi.ssimlla, with the difference 

 that only one gill is visible in the fissure over the neck. It is remark- 

 able that on the whole northwest coast of America, down to California, 

 no Patella, only animals of the genus Acmiva were to be met with." 



Jt will be noticed from the preceding documents that in the Alaskan 

 region fourteen species of Limpets, not counting the innumerable varie- 

 ties, and twenty-six or seven species of ChitonidcCj are known, most of 

 w hich have rewarded our researches, and a part of which are absolutely 

 new. Additional species may be expected to recompense additional 

 and more minute research; but that the chief members of these groups 

 native to this region have been determined there is little reason to doubt. 



* Prom the English reprint, published in tin; Hprin^ of 18: 10, but dated by the author 

 at "Dorpat, Jan. 7, 18v>8." I found the first edition in the Itoyal Library at Stock- 

 holm. It passed tin; censor in March, 1829, was issued in the winter of 1820-:J0, and 

 is dated on tho titlenago 1830. 



