402 THE CHICAGO ACADEMY OF SCIENCES. 



Jaw, Radula and Genitalia : Unknown. 



Range: Maine. A species of the Alleghanian division of the 

 Transition life zone and of the Nova Scotian region. As the species 

 has been so misunderstood and mixed with catascopium, apicina, etc.. 

 only those records are mapped which are known to be correct. No 

 authentic records are known outside of the state of Maine. The Con- 

 necticut record of Linsley and the British American references by 

 Bell and Whiteaves are believed to have been based on some form of 

 catascopium. 



RECORDS. 



Maine: Winnecook Lake, Waldo Co. (Berry) ; Maine (Anthony; Binney; 

 Griffith; Haldeman; Lea; Lewis; Mighels; Walker); Portland, Cumberland Co. 

 (Chickering) ; Unity, Waldo Co. (Adams; Mighels). 



Geological Distribution : Unknown. 



Habitat : "Adhering to boulders just below the surface of the 

 water." (Chambers). 



Remarks: Decollata is a very distinctive species, easily known 

 by its flatly sloping spire, tumid body ivhorl, somewhat patulous aper- 

 ture and very tightly closed umbilicus. It does not seem to be similar 

 to any species, excepting, perhaps, some short-spired forms of cat- 

 ascopium which, however, have a differently shaped spire, aperture 

 and umbilical region. The spire is decollated in a majority of the 

 specimens examined. 



Decollata seems to be little understood by most conchologists. It 

 has been placed in both catascopium and emarginata, and has also been 

 considered a variety of mighclsi. Specimens of apicina from northern 

 Michigan and Lake Superior have been identified as decollata and 

 specimens of emarginata angulata have also been so identified. This 

 confusion has arisen from lack of authentic specimens for comparison. 

 The specimen figured by Binney (fig. 37, ex Haldeman, Smith, No. 

 9132) is larger and much thinner than specimens believed to be typical. 

 This specimen measures as follows: Length, 21.00; breadth, 15.00; 

 aperture length, 14.00 ; breadth 10.00 mill. Mighel's original measure- 

 ments are: length, 15.00; breadth. 12.50 mill. This specimen has all 

 of the characteristics of decollata excepting that it is larger, thinner and 

 has a more patulous aperture. It is not mighclsi, as may be seen by 

 comparing the spire and body whorl with those of mighclsi, which are 

 much broader, rounder and of a different shape (compare Binney's 

 figure with figure 9 on plate XLI). Specimens in the Boston Society 

 of Natural History (No. 24192) which were deposited by Mighels 

 and may, indeed, be considered cotypes, agree well with Binney's 

 figure 37. Two of these are figured on plate XLI, figures 8 ond 9. 



