50 CELLULARIID^. 



But the most striking difference is found in the vibracu- 

 lar appendage, which in S. scabra is of a very remarkable 

 type, and totally unlike the form which prevails throughout 

 this genus. Instead of being erect, with a notch or cleft at 

 the top in which the movable seta works, it lies across the 

 back of the cell, its shape and structure reminding us of the 

 fixed base or beak of a sessile avicularium, while the seti- 

 form process is reduced in size and capability of move- 

 ment, and rather performs the part of a mandible than of 

 the vibraculum, wdth its free and vigorous swing. We can- 

 not fail to recognize in this modified structure a transi- 

 tion form between the avicularium and vibraculum, which 

 is of the highest morphological interest. In this species 

 the vibracula are commonly wanting on many of the 

 cells. 



Amongst the minor characters may be mentioned the 

 short spine which occurs at the top of the median cell at 

 each bifurcation of the branch. The internodes are shorter 

 than those of S. scrupea, but still of considerable length. 

 Specimens from Greenland are much stouter and more 

 massive that those from the Northumberland coast ; and 

 the species would seem to be specially a northern form, 

 though ranging to Madeira. 



SCRUPOCELLARIA SCRUPEA, Busk. 

 Plate VII. figs. 11-14. 



ScRUPOCELLARiA SCRUPEA, Biisk, Aimals N. H. ser. 2, vii. 83, pi. ix. figs. 11, 

 12; B.M. Cat. i. 24, pi. xxi. figs. 1, 2: Heller, Bryoz. 

 rl. Adriat. M. 10 (sep.) : Norman, Quart. Journ. Micr. Sc. 

 (n. s.) viii. 214 (3 Sep.). 



Zoarium erect, the shoots dichotomously divided, inter- 

 nodes much elongated. Zo<xcia biserial, alternate. 



