520 VESICULARIID^E. 



BowERBANKiA IMBRICATA, Johiist. B. Z. ecl. 2, 377, pi. Ixxii. figs. 5, 6 : 

 Alder, Northumb. Cat. loo. cit. 67 (sep.) : W. Thompson, 

 N. H. Irel. iv. 466 : Hincks, Dev. Cat., Ann. N. H. ser. 3, 

 ix. 473 (59, Sep.) : JoUct, Bryoz. d. cotes de France, 102, &c. 

 (Not B. imbricata, Gosse, Mar. Zool. ii. fig. 39.) 



BowERBANKiA DENSA, Favre, Phil. Trans. 1837, 391, pis. xx. & xxi. : Johnst. 

 B. Z. ed. 1, 255: Van Ben. Recb. 29, pi. iv. fig. A (Mem. 

 Brux. xviii.). 



Stem tubular, creeping {B. densa auctt.) or erect, and ir- 



; regularly branclied {B. imhricata) *. Zooecia large, ovato- 

 cylindrical, transparent, broad and squarish at the top, 

 somewhat narrowed below, disposed in groups along the 

 creeping stolon, or in irregular clusters (sometimes 

 almost continuously) on the erect stems and branches. 



Polypide with 10 tentacles, furnished with a row of about 

 12 tactile setae on the back : gizzard large and power- 

 ful. 



Height of the erect form 1-3 inches. 



In its erect form this species grows in " bushy, flaccid 

 tufts," much and irregularly branched, and attains a very 

 considerable size. The cells are arranged in large, dense 

 clusters along the stem, either on one aspect of it only, 

 or (not unfrequently) on all sides of it. Occasionally the 

 groups blend, and the zooecia range almost continuously 

 along the branches. The stem is stout and smooth, and 

 of a decided horn-colour. In its humbler form B. imbri- * 

 cata spreads on the surface of Algse, stones^ &c., the 

 cells being grouped at intervals on the creeping stolon. 

 The common Corallina is a favourite habitat ; and on 

 this it forms compact suborbicvilar tufts, which completely 

 surround the stem. 



* "Au printemps * * * on troiive abondamment la forme densa de la 

 Bowcrhankia compos^e d'une quantity de loges dressees sur la surface de I'Algue 

 et pressdes I'une contre I'autre de maniere a ne former qu'un tapis. Plus 

 tard se detacbent de ce groupe des stolons, puis des rameaux libres qui 

 poussent des branches et, se garnissaut de paquets de loges, reproduisent la 

 forme imbricata." — Joliet, Bryozoaires des cotes de France. 



