126 Proceedings of the Royal Irish Academy. 



2. Crisia geniculata^ Milne-Edwards. • 



Busk, Smitt, and Hincks consider tins only as a variety of 

 C. cornuta, but Harmer follows Milne-Edwards in regarding it as a 

 distinct species, differing in the form and position of the ovicell, and 

 in the total absence of spines. It is more slender and delicate than 

 C. cornuta, and the ovicell, which is not often found, is smaller, not 

 much inflated, and there are always one or more zooecia on the inter- 

 node which bears it. 



Irish localities. — Griandore Harbour (Eoy. Irish Acad.) : Dublin 

 Bay (J. E. Duerden). 



3. Crisia elurnea, Linn. 



This species, so far as any identifications yet go, appears to be the 

 commonest Irish form, and has been recorded from many localities ; 

 though, as Mr. Harmer mentions, " owing to the fact that it is often 

 impossible to distinguish species of Crisia without having the ovicell 

 to refer to," the name may easily have been given to other forms, such 

 as C. acideata or C. ramosa. The characteristic habit is that of the 

 branches being turned towards the axis, and closely massed together. 



I have met with a peculiar variety from Dublin Bay, in which 

 nearly all the internodes bear only three zooecia, some only two, and 

 others more. Mr. Harmer informs me that he has not found any quite 

 like my specimens from his collections ; but he refers to the fact, loc. 

 cit., p. 173, that G. "Winter has stated "that in the Danish forms of 

 C. eburnea from the brackish waters of the Baltic the internodes are 

 said to have typically only three zooecia ; in those most exposed to the 

 North Sea the internodes have seven zooecia, and in colonies from 

 intermediate localities there are five zooecia." He says, however, that 

 he himself has not been able to observe any such definite correlation 

 between the character of the colony and the conditions under which 

 they grow. My specimens were obtained from the sands along the 

 Bull-wall, Dublin Bay, washed up after a storm. 



Mr. William Thompson records this species as being common 

 on algse and zoophytes around the coast of Ireland. I have found it 

 amongst the Royal Irish Academy Survey's dredgings from Glandore 

 Harbour and Berehaven, and on several occasions from Dublin Bay. 



Irish Localities. — Clifden, Connemara (W. Thompson): Toughal 

 (Miss Ball) : Glandore Harbour (Roy. Irish Acad.) : Dublin Bay: 

 Berehaven (Roy. Irish Acad.) : Antrim and Down Coasts (Mr. 

 Swanston). 



