540 CYLINDIUECII]' 



It requires a keen and practised eye Fig. 30. 

 to detect it iu the muddy situations in 

 which it chiefly delights; and, indeed, 

 without a previous knowledge of its pe- 

 culiarities it is pretty sure to escape 

 observation or to be passed by as a weed. 

 The cells are rendered very dark-coloured 

 and opaque by the large quantity of earthy 

 matter imbedded in their walls. They are An e uinella P almata - 

 generally curved slightly inwards towards the stem ; they 

 are not contracted at the base, and have rather the appear- 

 ance of processes of the branch than of distinct cells. 



HABITAT. On shells, dead or living, stones, &c., between 

 tide-marks, especially in muddy situations and in shallow 

 water. 



LOCALITIES. River Deben, Suffolk, abundant on oyster- 

 shells ; Tenby, caves in St. Catherine's Isle, sparingly 

 (Busk) : Filey, between tide-marks (T. H.) : Ilfracombe 

 (Allman). 



GEOGRAPHICAL DISTRIBUTION. Ostend, very abundant, 

 especially in autumn (Van Ben.) : Charleston, South 

 Carolina (Dr. Harvey). 



Doubtful Species. 



NOLELLA STIPATA, GOSSC. 



NOLELLA STIPATA, Gossc, Mar. Zool. ii. 21, fig. 38. 



ZooBCia erect, subcylindrical, crowded on tubes which form 

 an undefined incrusting mat. Polypide with 18 ten- 

 tacles. 



Probably referable to Cylindroecium. 



