316 ESCHARID^. 



is elevated and thickened. The nodulous processes on 

 the sides are generally well developed in the fertile 

 cells, and stand out prominently in front of the ovicell ; 

 in other cases they are sometimes inconspicuous, and 

 sometimes wanting altogether. Very commonly the whole 

 peristome is slightly raised and thickened, with the excep- 

 tion of the inferior margin, which is always simple. 



It is not easy to determine the affinities of this species ; 

 but, in the absence of all striking features, the tall, arched 

 orifice, with the lower margin almost straight and entire, 

 seems to connect it with the present rather than with any 

 other group. 



Genus UMBONELLA. 



Der. From umbo, a rounded elevation. 



Lepkalia (part.), Johnston, &c. 

 DiscoPORA (part.), Gray. 

 EscHARA (part.), Smitt. 



Generic Character. — Zocecia ivith the primary orifice 

 suhorbicular or subquadrangular , lower margin slightly 

 curved inwards, peristome not elevated, no secondary ori- 

 fice ; a prominent umbo ( ? aviculai'ian cell) immediately 

 below the mouth, supporting an aviculai'ium. Zoarium 

 {in the British species) incrusting. 



In this genus the primary orifice remains unchanged, 

 as it usually does in Lepralia, but it exhibits a very dif- 

 ferent form from that which is characteristic of the latter. 

 It is wide, well-arched above, with the sides slightly 

 rounded, or somewhat compressed, and the lower margin 

 a little curved inward. It is now suhorbicular and now 

 decidedly subquadrangular, but it never makes any 



