130 



ually diverge, widening as they proceed, and assuming an 

 inclined position, until, approaching the front of the vaive 

 by a regular curvature, the lower edge has become anterior, 

 giving the band an angle of 30° with the plane of the shell : 

 approaching the median line, the band rapidly widens, and 

 the front margin is drawn forward in a long acumination, 

 while the inner margin is regularly concave, except that 

 near the median line it turns abruptly forward so as to meet 

 that line at an acute angle. The loop thus forms an urceo- 

 late figure on its inner margin, and on the outer a somewhat 

 oval one, truncated behind and attenuately acuminate be- 

 fore. In the median line where the two branches meet, 

 both are suddenly deflected downwards, forming a double 

 vertical plate, not quite reaching the ventral valve ; the 

 upper edge of which, when viewed from the side, is flatly 

 roof-shaped, while the lower edge describes two convexities^ 

 the greater anterior, leaving a notch between them. The 

 surfaces of the loop and median plate are covered with 

 minute obliquely conical pustules, in some places seeming 

 to become spinulous." 



Fig. 1. Fig. 2. Fig. 3. 



Fig. 1. Dorsal view of Cryptonella julia, showing the 

 loop and horizontal plate. 



Fig. 2. Profile view, showing one band of the loop with 

 the vertical plate. 



From drawings, four times enlarged, by Prof. Winchell. 



Fig. 3. front view of the loop. 



