A REVISION OF TH K GENUS STEGANOPOUELLA. 271 



of the tube. The median process in a is broader than long ; 

 in B longer than broad. Its border is not much everted, nor 

 with pointed distal corners; and its cavity is shallow. The 

 tube in b zooecia is usually surrounded by the cryptocyst, its 

 low lateral walls sloping down distally, so that the distal 

 border of the tube has no raised wall. In a zocccia the tul)e 

 is incomplute distally, though its wall may be more developed 

 than in tig. 11. The lateral recesses commonly have a par- 

 tial roof, formed by a thin upstanding calcareous lamella 

 continuous with the lateral wing of the median process, from 

 which it passes proximally and then forwards on the outer 

 side of the lateral recess. 



The epithecal sclerites are small and inconspicuous, sepa- 

 rated by a wide interval from the operculum. The b opercula 

 (fig. 38) are quite distinctive. They are of great size in pro- 

 portion to the A opercula; they are more or less quadrangular, 

 with rounded distal corners, and are usually longer than 

 broad. There are nineteen to twenty-four fine, long, sharp, 

 recurved teeth, borne on the distal half only of a thin sub- 

 marginal sclerite. The distal part of the A-shaped main 

 sclerite is formed of two long, prominent, parallel bars, the 

 loop between which is not much dilated distally. The chi- 

 tinous floor of this space ends at the proximal end of the 

 parallel portion, the space on the proximal side of its edge 

 between the diverging parts of the sclerite being triangular. 

 The occlusor tubercles are small. The proximal projections 

 are very prominent, and are somewhat everted with a con- 

 cavity on their inner sides. The basal sclerite is strong, and 

 the oblique sclerite well marked. 



The A opercula (fig. 39) are of the '' undifferentiated " 

 type, and closely resemble those of some of the preceding 

 species. 



The diameter of the a opercula in the type specimen («) is 

 about 490 /i, and that of the b forms about 520^. Tlie a 

 opercula of specimen e average about 350 /<, and the b forms 

 about 450/'. 



