452 Proceedings of the Royal Irish Academy. 



(_Halotlirix lumbricalis, Eke. 



This species not yet recorded for Ireland, forms tufts 1 incli 

 long, not unlike Elacliistea fiicicola or E. flaccid a, with lateral 

 accumulations, on old leaves of Zostera.] 



Giraudia, Derb. et Sol. 



G. s2)hacelarioides, Derb. et Sol. 10 N. 14 IS". 



This species grows on Zostera, Desmarestia aculeata, &c., 

 and might easily be mistaken by the naked eye for small 

 SpJiacelaria cirrhosa. 



Order YIII. — Sphacelaeiace^. 



In all the members of this group the cell- wall turns black on 

 treatment with eau de javelle. 



i. Sphacelahiace^ CEUSTACE-S. 



[_JBattersia mirahilis, Eke. 



This interesting species, looking like a Half sia, covered with 

 a microscopic Ectoearpus, is not yet recorded for Ireland.] 



ii. Sphacelaeiace^ genuine. 



S^ihacelaria, Lyngb. 



8. radicans, Harv. 12 H. + M. + D. 14 N. 

 S. olivacea, Pringsh. 12 M. 

 S. cirrhosa, C. Ag. 



On Desmarestia aculeata, etc., on all the coasts. 



/. fusca, Holm, et Batt. 12 N. 



Chaetopteris, Kiitz. 



Ch. plumosa {^Sphacelaria plumosa, Lyngb. in Harvey's Phyc. Brit., 

 pi. 87. Cladostephiis plumosus, Holm, in Alg. Brit. rar. No 1.) 

 12H. + T. 13 H. 



Cladosteplms, C. Ag. 

 C. spongiosus, C. Ag. 



On all the coasts. 

 C. verticillatus, C. Ag. 



On all the coasts. 



