ACADEMY OF SCIENCES. 271 



tcrior margin. Interior smooth, white, except the margins, which are polished 

 and of the same color as the exterior. Nacre, especially when weathered, sil- 

 very. Long. •3.'') in., iat. -27 in., alt. •12 in. of largest specimen. 



Dead on beach, east side of Simeonoff Island, Shumagins. Living, proba- 

 bly on fiici — off shore. (Plate 1, fig. 2). 



This, from its appearance, is probably a true Nacella, congeneric with the- 

 Cape Horn species, and the first described from the northern hemisphere. Its 

 occurence with that of several other mollusks in the Aleutian fauna is remark- 

 able ; and the facts, on further insp'.'ction, have developed a considerable resem- 

 blance between these antipodal fauniE. 



Littonna aleuticn, Dall. Shell depres.sed, whorls four, the nucleus including 

 one and a half. Last whorl much the largest ; spire depressed or nearly flat- 

 tened. Color variable, from dark brown or purple to waxen white, or banded 

 with white on a darker ground. Nucleus polished, dark brown, translucent. 

 Sculpture consisting of rather coarse lines of growth, and about six or eight 

 nodulous revolving ridges more or less strongly elevated in different specimens, 

 the three middle ones being the most prominent, and faint revolving lines being 

 also traceable occasionally between the ridges. Aperture very oblique, smooth, 

 white or purplish within, outer lip sharp, columella broad, straight, generally 

 with a chink behind it. Anterior margin a little produced. Long. -41 in., Iat. 

 •53 in., of an average specimen. Animal and operculum precisely as in L. Sit- 

 kana, which was abundant on the same rocks. Hab. Living at Gull rocks 

 Akutan Pass, Aleutian Islands, abundantly. — W. H. Dall. 



This is a very remarkable and distinct species, resembling no other on the 

 West American coast. (Plate 1, fig. 3). 



Notes. — Buccnmm Kennicottii, Dall, proves on obtaining specimens contain- 

 ing the soft parts and the operculum, to be a C/trijiodomus. It was originally 

 described as a Buccinum, in deference to the ojiinion of the late Dr. William 

 Stimpson, who had recently monographed the northern species of that group. 

 Its distribution is from the Shumagins eastward, not as was originally reported 

 from Unalashka. 



Buccinum Baeri, Midd. proves to be a very marked race of B. cijaneum. B. 

 Fischerianum. Dall, which was suspected at the time it was described to be 

 similarly related to B. cijancum, proves to be distinct. 



Haliolis, which has long been tabulated as an inhabitant of the Aleutian 

 chain, does not exist in that part of the archipelago east of Unalashka, aLd 

 probably not in these islands at all. 



A partial comparison of the Conchology of portions of the At- 

 lantic and Pacific coasts of North America. 



BY ROBERT E. C. STEARNS. 



A striking feature in the Conchological fauna of that part of the Pacific 

 coast included in the Califoruiau and Vancouver Zjological province when 



