THE NAUTILUS. 109 



upper and lower palatals regular, an interpalatal in many specimens; 

 suprapalatal wanting or quite small. 



Alt. 3.5-4 (rarely 3.2-3.4), diam. 1.9-2.1 mm.; aperture alt. 1.5, 

 diam. 1.2 mm. 



Soft parts, seen only from one dried Alabama specimen, soaked, 

 very dark from copious, deep brown pigment. Jaw amber-colored, 

 strongly curved, rather broad, rounded at the ends, its surface with 

 numerous radial rib-striae; the line of the attachment of the tenacu- 

 lum strong. 



Radula with 78 transverse rows of 27 (or 29) teeth, r + 6 + 7 (8); 

 rachidian rather narrow, with a short mesodont and very small ecto- 

 donts (barely visible); laterals bicuspid, with the mesodont as long as 

 the plate, the ectodont about one-third as long; the outer posterior 

 angle of the plate raised, cusp-like; seventh and eighth with the 

 ectodont split in two, somewhat intermediate or '• transition " teeth; 

 marginals (9-13) serrate, with the mesodont rather long, thin; the 

 fourteenth a barely visible irregular transverse bar, or wanting. As 

 this is from a single specimen, there may be some variation. Other 

 parts could not be examined. 



Habitat: Knoxville (various localities); eastern Tenn.; Fayette- 

 ville and Columbia, Tennessee; Gurley and Huntsville, Alabama; 

 Grand Rapids, Michigan; " Ottawa, Illinois."? 



The species shows little variation, except in altitude, with nearly 

 the same diameter, and such as are noted in the description. There 

 is no tendency towards having the peristome continuous. The types 

 are from Knoxville, Tenn., but almost any good specimen seen from 

 anywhere might be taken for a type. 



B. clappi is remarkable for its resemblance to some forms of B. 

 armifera Say, for a variety of which it has been taken. Yet it is 

 quite distinct. Ot over 150 specimens carefully compared with more 

 than 1500 armifera not one was found doubtful or intermediate. 

 The most tangible difference is in the shape of the columellar lamella. 

 The shell averages somewhat smaller, the apex is more acute, the 

 surface striae are finer and slighter, the lower palatal plica is always 



^ B. armifeTa shows considerable variation with respect to size and shape, 

 and in connection with it, in the shape of the columellar and lower palatal. 

 These differences mark two main forms, varieties at least, the shell of one of 

 them being more cylindrical aud more or less resembling clappi, but the colu- 

 mellar (and lower palatal) are always different. 



