Maryland Geological Survey 395 



lower port, with frequently a slight mucronate extremity, which when 

 broke]i generally shows a slight central perforation, as do many of those 

 which are destitute of this pointed extremity. In many old examples the 

 extremity is solid .... while in the largest individual which I have 

 observed from New Jersey .... there is yet a slight perforation. 1 

 have never seen the mucronate point exceeding one-sixth of an inch in 

 length. The upper end of the stylet or guard, from about the base of the 

 internal cavity, gradually expands upward and becomes very thin on the 

 edge, and the inner surface of the wall often bears the marks of the 

 transverse septa of the phragmocone. At about the base of the cavity the 

 external diameter is less than below, and in some examples the lower 

 portion is considerably expanded as in the .... typical specimen of 

 Dr. Morton's var. A B. suffusiformis, while in others there is almost a 

 regular decrease downward to near the extremity, which is usually obtusely 

 rounded except for the mucronate point occasionally seen. Very young- 

 specimens often present a long slender extremity. On the ventral side, 

 the slit extends fully one-third of the length of the shell, where the walls 

 of the upper portion are preserved to near their full length, which is 

 seldom the case; its width in the lower half often being little more than 

 the thickness of heavy writing paper. The flattening of this side of the 

 stylet commences near the base of the slit and extends almost to the lower 

 extremity of the guard. On the dorsal side there is a raised elongate 

 lanceolate area, which is narrow and prominently angular in the upper 

 part of the body, but is flattened or simple depressed convex on the sur- 

 face and gradually widens below the base of the slit so as to become from 

 half the entire width of the shell to almost its equal in width, but pro- 

 duces a slight angularity on this side throughout the entire length. The 

 entire surface is usually much roughened when not worn, the roughening 

 being greatest on the ventral side, while laterally this roughening produces 

 vascular lines running obliquely backward in crossing from the ventral to 

 the dorsal surfaces, and on the raised lanceolate area of the dorsal surface 

 the markings are finer and arranged so as to produce longitudinal lines, 

 or interrupted stria? 



