) 



ALGJS OF WEST IRELAND. 159 



tADiosuM, Wolle. (Desm. TI. S. p. 90, tab. 19, 



Long. 55 fi ; lat. 45 fx ; lat. isthm. 12 /x. 



I. Creggan Lough. 



86. C. speciositm, Lund, var. simplex, Nord. (Desm. Spetsb. 

 p. 31, tab. 6. fig. 12.) 



II. Carrantuohill. 



87. C. subspeciosum, Nord. (Desm. Arct. p. 22, tab. 6. 



fig. 13.) 



I. Creggan Lous:h. 



minor, Wille. (Ferskv. Alq. ft 



Nov. Semi p. 36, tab. 12. fig. 17.) 



Long. 28 jjl ; lat. 20// ; lat. isthm. 15// ; crass. 11 p. 



TV 



89. C. orbiculatum, Rolfs, in Annals of Nat. Hist. vol. xiv. 

 p. 392, tab. 11. fig. 2 ; Brit. Desm. p. 107, tab. 17. fig. 5. 



Long. 35 /x ; lat. 19 /* ; lat. isthm. 8 /i. 

 I. Ballynahinch. — II. Carrantuohill. 



90. C. isthmium, West. (Fr. Wat. Alg. of North Wales, 

 p. 290, pi. 5. fig. 19.) [C. excavatum, Nord., f. duplomajor, 

 Lund (Desm. Suec. p. 46) ; Wolle (Desm. IT. S. p. 77, pi. 53. 

 figs. 14, 15) ; Wille (Ferskv. Alg.f. Nov. Semi. p. 47).] 



ft Forma hibernica. (PI. XXI. fig. 15.) 



Forma major, angulis inferioribus rotundatioribus, isthmo 

 latiore ; pyrenoidibus singulis et magnis. 



Long. 50-53 /x ; lat. 31m; lat. isthm. 19-21 /i. 



I. Ballynahinch. — II. Sugar Loaf Mt. ; Castletown ; Glen- 

 gar riff. 



The dimensions of the Welsh specimens here considered as 

 type were : — Long. 40 /jl ; lat. 25-26 /* ; lat. isthm. 11 ft. 



Although this species has been placed under C. excavatum, 

 Nord. (Desm. Brasil. tab. 3. fig. 25), by several writers, it is 

 distinct. C. excavatum is much smaller, and it is much longer 

 relatively, moreover the form of its median excavation is so 

 different. Mr. Bennett (Jouru. Royal Micr. Soc, June 1890, 

 p. 305), reasoning from the figure and description, considers it 

 a8 a dividing form of C. orbiculatum, Ralfs; however, many 



