162 Trans. Acad. Sci. of St. Louis. 



Camarophorella lenticularis (W. & W.). 



PL XIV. f. 11-13. 



Original description. ** Shell small, broadly ovate, or sub- 

 circular, length and breadth nearly equal, profile lentiform. 

 Valves subequal, depressed convex. Beaks small, pointed, 

 slightly incurved, sides and front regularly rounded. Pedicle 

 valve a little the most convex ; the beak pointed, and project- 

 ing beyond that of the dorsal. Spondylium of the interior 

 of the ventral valve proportionally large, in some specimens 

 nearly one- third the width of the shell, and extending about 

 one-third the length of the valve ; longitudinal septum reach- 

 ing to near the center of the shell. Interior of brachial valve 

 with a single longitudinal septum, with horizontal plates curv- 

 ing toward the cavity of the opposite valve. Strong radiat- 

 ing muscular or vascular markings appear on internal casts of 

 both valves," 



** Surface apparently smooth, without mesial fold or sinus." 



Length of an average pedicle valve 12 mm., breadth 10\ 

 mm. ; dimensions of a brachial valve, length 10|^ mm., breadth 

 12 mm.; thickness of a specimen 11 mm. long and 10 mm. 

 wide, 6 mm. 



Dielasma allei (Win.). 



PL XIV. f. 10. 



Centronella allei. Bull. U. S. G. S. 153: 171. 



Original description. ** Shell large to medium size, tere- 

 bratuliform, greatest width a little anterior to the middle, 

 contained one and one-fourth times in the greatest length. 

 Pedicle valve somewhat ventricose, full to the immediate 

 vicinity of the margin, especially along the cardinal slopes ; 

 regularly arching from beak to anterior margin ; highest in 

 the middle ; anterior margin with a barely perceptible trunca- 

 tion ; no sinus or fold present ; beak produced beyond that of 

 brachial valve, truncated and circularly perforate at the 

 extremity ; dental lamellae more than one-fifth the whole 

 length of the valve ; muscular scars, consisting of one faint 

 median linear impression, on each side of which is another, 

 all reaching to the middle of the valve. Brachial valve with 

 its short imperforate beak closely concealed under that of its 

 fellow, slightly truncate in front, but without mesial fold or 



