284. THE CHICAGO ACADEMY OF SCIENCES. 
Length. Breadth. Aperture length. Breadth. 
13.50 6.25 7.00 3.10 mill. Type 
15.00 6.00 6.00 Spy 7 
14.00 6.00 6.50 3505) 
als tis) 6.00 6.50 Sea 
12.50 6.00 6.50 3.00 “~  Cotypes 
13.50 6.00 6.50 300 ae "a 
12.75 6.00 6.25 S00) i 
13.50 6.25 6.50 Se) Maine 
Types: Coll. Bryant Walker, eight specimens, No. 20040; co- 
types, Chicago Academy of Sciences, five specimens, No. 23968 ; Acad- 
emy of Natural Sciences, Philadelphia. 
Type Locariry: Headwaters of the Union River, Ontonagon 
County, Michigan. 
ANIMAL: Not differing from that of obrussa. 
JAw and Rapurta: Same as those of obrussa. 
GENITALIA: Similar to those of obrussa (Maine specimen). The 
retractor muscle of the penis-sac differs in being much larger, fan- 
shaped, with numerous branches at either end. (Pl. XIV, fig. G, 3.) 
A specimen measured as follows: 
Prost. Ret.mus. Ret.mus. Rec. sem. 
Penis. Penis-sac. Vas. def. duct. penis. penis-sac. duct. Shell. 
2.00 2.00 5.00 1.00 1.00 1.00 1.00 13.50 
Rance: Northern Maine to northern Michigan. Southern Boreai 
and northern Transition (Alleghanian) life zones. Canadian and Nova 
Scotian regions. Further search will probably reveal this variety in 
many other localities in the northern part of the United States. 
RECORDS. 
MAINE: Unity, Waldo Co. (Berry); Thomaston, Kngx Co. (Lermond). 
MicuicAn: Union River and Little Iron River, Ontonagon Co.; Salmon 
Trout River, Marquette Co.; St. Mary’s River, Sault Ste. Marie, Chippewa Co. 
(Walker); rock pools of Middle Branch, Lake Superior, Ontonagon Co. 
(Walker and Ruthven). 
GEOLOGICAL DistRiBUTION: Unknown. 
Ecotocy: “Occurs quite numerously in the rock pools of the 
middle Beach.” (Walker and Ruthven. ) 
RemArRKS: This variety differs from typical obrussa in being 
more slender, with a longer, more turreted spire, deeper sutures and 
a more oval aperture. The body whorl is more cylindrical than in the 
typical form. Mr. Walker says: “It is apparently characteristic of 
the small rivers tributary to Lake Superior. With the exception of 
a few specimens from Sault Ste. Marie, the typical form has not been 
as yet found in the upper peninsula at all. As a characteristic loca! 
form of a large region, it seems worthy of a name.” The specimens 
