( JC) 13HIT1SH 



This variety is widely distributed in the British Islands, 



' V 



and several distinct forms of it can be recognized apart from 

 the one originally figured by Kali's. Two of these we have 

 named as follows : 



Forma LATIUSCULA (PI. CXIV, fig. 5). Cells proportionately 

 wider and isthmus broader; spines shorter. Length 18 

 20/Lt; breadth without spines 19-23/*, with spines 31-34 /n; 

 breadth of isthmus 9 10 ju. 



Forma SUBHEXAGOXA (PI. CXIV, fig. 6). Smaller; seinicells 

 subhexagonal-elliptic, spines very short. Length 15'4/u; 

 breadth without spines 15 /u ; length of spines 3-3*8 fj. ; breadth 

 of isthmus 7*5 p. This form has been described and figured 

 as A. Incus var. Ralfftii forma spinis brevissimis W. & G-. S. 

 West/Further Contrib. Freshw. Plankton Scott. Lochs/ 1905, 

 p. 501, t. 7, f. 10. It would appear also to be identical with 

 Staurastrum dejectumftreb. v&T.Debaryanum (Jacobs.) Xordst. 

 forma Borge, 'Beitriige Alg. Schweden/ 1906,, p. 44, t. 3, 

 f. 36. 



Var. validus W. & G-. S. West. (PI. CXIV, figs. 9, 10.) 



.4. Incus var. validus AY. (I. 8. West, Some Desm. U. S. 1898, p. 320, 1. 17, 

 f. 16; Freshw. Alg*. Cevloii, 1902, p. 192; Cushmaii in Rhodora, vii, 

 1905, p. 260. 



Cells laro-e ; semicells obversely subsemicircular 



o / 



Avitli an almost straight apex; spines very stout and 

 long, strongly divergent. 



Length without spines 33-o ")//,, with spines 84- 

 IJljit; breadth without spines 29-3 (5 /x, with spines 

 50-76 p. ; length of spines 27-42 p. ; breadth of isthmus 

 8'5-9/x. 



SCOTLAND.- -Khiconich, Sutherland ! 



IRELAND.- -Xear Foxford, A Iayo ! 



Geor/r. Distribution.- -Ceylon. United States. 



This is the stoutest of the varieties of ^1. Incns } and in the 

 largest forms the bases of the spines are hollow (consult 

 PL CXIV, f. 9). 



Var. longispinus Eichl. & Eacib. (PI. CXIV, fig. 8.) 



A. Incus Wolle, Desm. U. S. 1SS4, t. 24, f. 3. 



A. Incus forma longispina Eichl. & Racib. in Rospraw. Spraw. Wydz. 



matem.-przyr. Akad. Umiej. Krakow, xxvi, 1893, p. 120, t. 3, f. 21. 

 A. Incus var. longispinus W. & G. S. West, Further Contrib. Freshw. 



Plankton Scott. Lochs, 1905, p. 501, t. 7, f. 22 ; Ctishman in Rhodora, 



vii, 1905, p. 260. 



