536 CYLINDIUECIIIXF,. 



CYLINDRCECIUM DILATATUM, Hincks. 

 Plate LXXVII. flg. 1, 2; Plate LXXIX. figH. 1-3. 



FARRELLA DILATATA, Hincks, Proc. Dubl. Un. Zool. & Botan. Assoe. ii. pt.l 

 (1860), 78; Q. J. Micr. Sc. viii. 279, pi. xxx. fig. 7. 



AVKNELLA DILATATA, id. Dev. Cat., Ann. N. H. ser. 3, ix. 473 (60, sop.). 



FARRELLA FUSCA, Busk, Q. J. Micr. Sc. iv. 94, pL iii. fig. 6. 



AVENELLA FUSCA, Alder, North. Cat. 69 (sep.) : Norman, Shell. Polyz., Rep. 

 Brit. Asaoc. 1867,311. 



VESICULARIA FUSCA, forma SIMPLEX, Smitt, loc. cit. 503 and 524, pi. xii. fig. 38. 



Stem slender, anastomosing, dilating at intervals into an 

 expansion, which forms the basal part of the cell, and 

 from which the erect tubular portion rises ; this expan- 

 sion is frequently set round with spinous processes. 

 Zocecia rather distant, tubulous, of moderate length, 

 decumbent towards the base, the walls opaque, having 

 the appearance of being sanded over with very minute 

 particles. 



Polypide with about 18-20 tentacles. 



THIS form has been identified by most recent writers on 

 the Polyzoa with the Avenella fusca of Dalyell, with which 

 (as I have pointed out in the account of that species) it 

 has no close affinity whatever. 



It is distinguished from C. giganteum not merely by 

 the size of its cells (which, though very variable, are 

 always much smaller than those of the latter species) , but 

 more markedly by the expansion of the creeping stolon, 

 constituting the basal portion of the zocecium. The 

 ectocyst is also less laden with earthy matter, and there- 

 fore much less opaque and coarse in appearance than that 

 of C. giganteum. The cell is of about equal size throughout, 

 and is continuous below with the expansion of the creeping 

 stem, which is a striking characteristic of the species. 

 This varies, to some extent, in size and figure. When 



