42 



SIXTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



of tlie valve by a regular curvature, the lower edge has become 

 anterior, giving the band an angle of 80° 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 urceolate figure on its inner margin, 

 and on the outer a somewhat oval one, truncated behind and 

 attenuately acuminate before. 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 pu- 

 stules, in some places seeming to become spinulous." 



Fig. 1. 



Fig. 2. 



Fig. 3. 



Fig. 1. Dorsal view of Cryptonella (Centronella) julia, showing the loop and horizontal plate. 

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

 Fig. 3. Front view of the loop. 



1 & 2 are from drawings, four times enlarged, by Prof. Winchell. 



Fig. 4. 



Fig. 5. 



Fig. 6. 



Fig. 7. 



Figs. 4 & 5. Ventral and dorsal views of a cast of a more oblate form of Cryptonella julia, 

 enlarged to correspond with figs. 1 & 2. 



Figs. 6 & 7. Ventral and dorsal views of C. meta, from the Schoharie grit. 



Fig. 4 is given simply to show the dental lamellas of the ventral valve. 

 The delicate impressed line in the centre, and a fainter one on each side, 



