UMBONELLA VERRUCOSA. 317 



approach to the semielliptical and laterally constricted 

 form which characterizes Lepralia. The hollow urabo- 

 nate rising below the mouth, on which the avicularium L 

 borne, is also, I believe, properly accounted a character 

 of considerable (secondary) importance. It is as wide as 

 the inferior margin, and extends for some distance over 

 the front wall of the cell. The avicularium is placed in 

 the centre of its inner aspect, resting on the lower lip of 

 the orifice. This umbo may be regarded as a partially 

 aborted cell, and is probably the equivalent, as I have 

 elsewhere stated, of the chamber below the primary orifice 

 in the genus Porella. 



The Arctic form which Sraitt describes as Eschara 

 verrucosa, can hardly, I think, be the same as Lepralia 

 verrucosa of Johnston and Busk. He speaks of the 

 elevated sides of its peristome, and describes them as 

 uniting with the margin of the ovicell, which, as he 

 expressly states, is imperforate. These characters do not 

 belong to our British form, which also exceeds the Arctic 

 very considerably in size. In his latest paper, Smitt 

 ranks his Eschara verrucosa as a " form " of Porella 

 compressa, which seems to show pretty clearly that it 

 must be quite distinct from the British species. 



UMBONELLA VERRUCOSA, Esper. 

 Plate XXXIX. figi. 1, 2. 



?CELLKPORA VERRCCOBA, Esptr, Cellep. pi. ii. figs. 1, 2. 



LEPRALIA VF.RRCCOBA, W. Thompson, Ann. N. H. xiii. 441 : Johnst. B. Z. 



ed. 2, 316, pi. In. fig. 3: Busk, B.M. Cat ii. 68, pi. Ixxxrii. 



figs. 3, 4, and pL xcir. fig. 6 : Helltr, Bryoi. d. Adriat. M. 



27. 

 LEPRALIA RKTICULATA, Courk, Corn. Faun. iii. 117, pi. ixii. fig. 9. 



