TUBULIPOEA. 271 



tata; at times, however, on stones and shells from deep 

 water. It is occasionally cupped, but more generally it is 

 shallow, like a saucer. Its largest size is about half an 

 inch ; with us it is less. It is calcareous and snow-white. 

 The margin is plain and entire. The series of tubes or 

 cells nearest the margin have plain angular apertures, like a 

 honey-comb. The inner cells are tubular, and in rows. 



2. TUBTJLIPORA HISPIDA, Cordiner. 



Hab. Parasitical on Flustrce and other seaweeds; also 

 on shells and rocks. With us, on the west coast of Scot- 

 land, T. hispida, in its common form, is far from being 

 rare, and it is got most frequently on Delesseria sanguinea ; 

 but larger and finer specimens are found, at times, on the 

 roots of the large tangle and on shells from the deep. The 

 broadest specimens I have met with were on Pinna ing ens, 

 from the island of Tiree. I have a special regard for this 

 little zoophyte, as it gave rise to what has been, to me, a 

 very pleasant and profitable correspondence with my excel- 

 lent friend, Dr. George Johnston, the well-known author of 

 the ' History of British Zoophytes/ and many other valuable 

 works on different branches of Natural Science. When he 

 was preparing his first edition of the ' History of Zoophytes/ 

 he wrote to me, saying, that he had observed, in my ' New 



