SOME NORTH AMERICAN DESMIDIE.E. 250 



inferioribus spina longa valida singula convergente instructis, angulis sup(M-ioril)U9 

 spinis duabus longis validis subdivergentibus instructis ; a vertice visaj triangulares, 

 lateribus concavis, angulis truncato-retusis, spinis longis validis tvil)iis subdivt'vgcn- 

 tibus prgeditis ; niembrana glabra. 

 Long. 30 ill ; lat. s. spin. 35 n, c. spin. 7i n ; lat. isthm. 14*5 ^. 



This differs from S. frificrcatum, W. B. Turn. (Freshw. Alg. of E. India, p. 110), and 

 var. reversmn, W. B. Turn. {L c. t. 17. lig. 9), in its relatively longer and straigliter 

 spines, in its very different sinus, its sborter length, and its concave sidps in vertical view 

 without any constriction below the angles. 



S. brasiliense, Nordst., var. triquetrum, Wolle (Alg. U.S. p. 4(1, pi. GO. iigs. 3!), 10), is 

 probably the same species as this, but his figure is not sufficiently clear to determine 

 the point ; it certainly is not a variety of S. hrasilieme, Nordst. 



121. Staueastrijm brasiliense, Nordst. in Vidensk. Meddel. 1869 (1870), p. 227, t. 1. 

 fig. 39. 



Var. LuNDELLii, nov. var. [S. brasiliense, Nordst. forma ; Lund. Desm. Suec. p. 73, t. 5. 

 fig. 2; Cooke, Brit. Desm. pi. 61. fig. 2.) Var. duplo-major (interdum subduplo- 

 major), cellulis quam spinae paulo longioribus, dorso rectis vol levitcr convexis, a 

 vertice visis 5-gonis (rarissime 6-gonis) ; raembrana minute scrobiculata. 

 The following represents the dimensions of one of the larger forms : — 

 Long. s. spin. 83 n, c. spin. 135 ix ; lat. s. spin. 80 n, c. spin. 141 ^; lat. isthm. 35 /it. 

 The plant which we have seen commonly from N. America, Ireland, and N. Wales is 

 sufficiently different from the Brazilian type to rank as a distinct variety. Two of the 

 three spines at the angles are generally placed horizontally, and the third is inserted 

 above them at an angle. The cavity of this Staiwastrmn is only mamillate within the 

 base of the spines, and does not project almost to the apex as shown by Wolle (Desm. 

 U.S. pi. xlviii. figs. 1-3). The figure by the latter of the front view is erroneous. 



Cooke's figures of both front and vertical views are very bad representations of British 

 examples ; his front views also show but two spines at each angle instead of three. 



122. S. CLAViFERTJM, uov. sp. (PI. XVI. fig. 25.) S. mediocre, paulo longius quam 

 latius, profunde constrictum, sinu aperto acutangulo ; semicellulae su])elliptica?, 

 dorso quam ventre convexiores, spinis brevibus validis numerosis in lineis subregu- 

 lariter ordinatis instructse, ad angulos cum spinis tribus (fere) longioribus, sine 

 spinis in sinu, apicibus subglabris ; a vertice visa? triangulares, lateribus retusis, 

 angulis subrotundatis, cum spinis brevibus subirregulariter ordinatis, ad angulos 

 longioribus ; glabrae in centro. 



Long. s. spin. 38-40 /t ; lat. s. spin 36-38 ^, c. spin. 42-44 ^i ; lat. isthm. 10-5-12-5 ^. 



At first we considered the species to be S. Bavenelii, Wood, 1873 (Wolle, Desm. U.S. 



p. 143, pi. 52. figs. 7, 8 [=S. sparsiaculeatum, Schmidle, 1895]), to which it is very 



.closely related. After examining a number of specimens, however, and finding constant 



differences between them and the figure of Wolle, we thought it better to define what 



xwe have seen as distinct. 



