250 AMERICAN JOURNAL 



The minute uncinus is very hard to find and quite variable in 

 form in this species. With care it may be^ detected, however. 

 This species comes as far south, on the west coast, as Sitka. 

 Here I found it, as well as the variety alveus, in great plenty, 

 but of small size. It can pretty readily be distinguished from 

 C. patina and, at Sitka, occupies a totally different station. 

 There all the other limpets are found alive only in the vicinity 

 of tide marks, but the testudinalis is to be found only in from 

 six to fourteen fms. (south-west of the fish house on the point), 

 on a weedy, gravelly bottom, overgrown with Zostera and Lami- 

 naria. Here all the conditions of ice cold water, stones for the 

 normal form, and weeds for the variety alveus abound ; while 

 not another species is found in the vicinity except Lepetido' and 

 other deep water forms. Every gradation from the typical 

 alveus to the typical testudinalis may be obtained. The animals, 

 dentition and shells agree in every particular with those from 

 Grand Manan (Stm.), New Bedford (J. H. Thomson), and 

 Beverly, Mass. (Dall), with which I have compared them. 



To the north it may be found in deep water among the Aleu- 

 tian Islands. I obtained dead ones on the beach of St. George's 

 (Pribyloff Ids) Bering Sea, and on Norton Sound and northward 

 it is the only species. It is best known from the North Atlantic, 

 where it abounds, but no specimens have been obtained, so far as 

 I know, from the Arctic Sea between Lon. 75° and 160° E. of 

 Greenwich. Some interesting facts in regard to migrations of this 

 species are given by Forbes and others. 



The position of the gill was not well understood by Williams 

 and Jefireys. It is situated on the left side of and above the 

 head, and extends across to the right ; most figures give an 

 erroneous idea of its construction. The uncinus is very small, 

 and sometimes abortive on some parts of the radula. I have 

 clearly distinguished it, however, in many instances, and it can 

 almost always be found with a high power. 



CoLLiSELLA PERSONA, Esch. sp. Plate 14, fig. 8. 



Acmma persona, Esch., Zool. Atlas, v, p. 20, No. 9, pi. xxiv, 

 f. 1 and 2. + A. radiata, Esch., ib. No. 8. + A. a^i- 

 ci/his, Esch., ib. No. 10, pi. xxiv, f. 4—6. + A. digi- 

 talis, Esch., ib. No. 11, pi xxiii, f. 7, 8. 

 Acmoia umbonata, Nutt., + Oregona, Nutt., + textilis, Gld. 

 Soft parts entirely cream color, except upper part of mantle 

 edge. Foot oval, longer than the body, hiding the head ; sides 

 smooth ; mantle edge narrow, thickened, upper surface with a 

 few^ faint macul?e of color like the margin of the shell; smooth, 

 finely ciliated. Head small, wide; tentacles short, thick, stout; 



