KONGL-. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:0 5. 99 



Long. 37, lat. 27, lat, isth. 10 ,«. T. IX, f. 9. 



I referred this and Cbä. sp. (C. puteale, No. 125) to Dr Nordstedt, who remarks 

 »the differences between certain Cosmaria and Xarithidiä are wery small, ... I have 

 often thought that we must again take lip Reinschs genus Didymidiutnv (a very 

 multifarious genus!); and I must own that this might just as correctly be called Cos. 

 xanihidiforme as by the above name! Gfr suggestion by me as to sub-genera. 



[In the dimensions of this genus, long, and lat., the spines are included]. 

 X. cristatuni, Bréb. (in Ralfs Br. Desm. p. 115, t. XIX, f. 3 a, b, c). 



Long. 80, lat. 70, lat. isth. 10, long. spin. 14—17 u. T. XII, f. 20. 



F. inornata, n. f. F. ventre vix inflato; membrana punctata. 



Long. 74, lat. 68, lat. isth. 15. long. spin. 10—12 u. Fig. 18. 



Var. leiodermuni. Minor; semicelluhe distincte octagonse. (Å\ leiodermum Roy & 

 Bisset, Jap. Desm. t. 268, f. 11). 



Long. 78, lat, 65, lat. isth. 14, 1. spin. 10—14 ,«. Fig. 33. 



— — F. irresjularis. F. spinis lateralibus irregulariter positis. 



Long. 84, lat. 70, lat, isth. 11, 1. spin. 10—13 ,u. Fig. 31; T. XIII, f. 3, 

 oblique. 



F. inevoluta. Fere ut in T", leiodermum, sed apice et basi spinis singulis, an- 

 gulis superioribus lateralibus spinis geminatis, armata. 



Long. 76, lat. 64, isth. 13, 1. spin. 11 ,</. T. XII, f. 27. 



Var. erectum. SemicelluUe margine superiore indistincte 4-angulatee, fere semi- 

 circulares, spinis dorsalibus erectis. 



Long. 74, lat. 76, lat. isth. 14, 1. spin. 12—14 ,«. T. XIII, f. 5. 

 X. bisenarium, Ehr. (Verbr. Amer. pp. 46, 51 et 138, »Icon Baileyi, 1841»; Euastnoi) 

 No. 11, Bailey Am. Bacill, p. 291, t. I, f. 13; A. cristatitm /? uncinaturn, et X. unci- 

 natum, Bréb. in Ralfs Br. Desm., p. 115, t. XIX, f. 3 d e f. 



F. typica. Angulis basalibus 1 — 2 aculeatis. Long. 82, lat, 68, lat, isth. 16, 1. 

 spin. 9— 11 fi. T. XII, f. 30. 



Var. rotuiHlatum. Seinieellulae rotundato-octagona\ non elongatse. 



Long. 70, lat, 54, lat. isth. 16, 1. spin. 6—11 ,«. Fig. 28. 



Var. ornat lim. Seniicelluhe paullo protensie, granulis et tuberculis 5 — 6 supra 

 protuberantiain centalem curvatiin dispositis; a latere bi-ovale, modice constrictum, 

 apicibus rotundatis. 



Long. 70—80, lat. 62—76, lat. isth. 13, cniss. 25, 1. spin. 10 ,u. T. XIII, f. 2. 



I can hardly coincide with the usual view that this is but a sub-species of X. 

 cristatum, as the form of the cells and the direction of the spines so widely differ 

 from that plant, moreover Fhbenberg's name has decided priority. The form described 

 by Wolle (Desm. U. S. A. p. 93, t. XXIII, f. 7 — 9) is certainly X Brebissdnii, Ralfs, 

 and not A', bisenorium. I a ni aware that I am venturing to differ with various 

 learned authors respecting this species, but, as I have manv speciinens of X. cristatum 

 with basal aculei hinary, I can but accept Ehrenberg's rernark, especially as the form 

 of fron<l (a greater point than one spine more or less!) agrees with the figures cited 

 of Ralfs & accepted by Brebisson. 



