On some new and rare Desmids. By W. B. Turner. 939 



to name it " var. Americanum." Mr. WoUe states that the sides 

 are convex, but they are frequently concave in the type ; and the 

 typical form bears larger and fewer spines, and is not so regular in 

 outline as the above. I find that the typical form is found in 

 America, and give figures of specimens from Minnesota and Nova 

 Scotia. Their dimensions are long. 52-62 fx = • 00205- • 00244 in. ; 

 lat. 52 /A = • 00205 in. ; lat. isthmi 17-18 ix = ■ 00067-7 in. 

 Ealfs gives lat. isthmi as 30 -5-34 -5 fjul Mr. Wolle, loc. cit. 

 p. 148, remarks on the variability of this species, and gives the 

 diameter as 45-50 fj,. Figs, 22a, h. 



23. S. dejecium Breb. var. 8udeticum Kirchner (Krypt. Flor. 

 V. Schlesien, p. 169). This rare and curious form has only before 

 been noted by Kirchner from Germany. So far as I am aware it 

 has not been figured. Minnesota, U.S.A. 



Long, 26 ij.= -00102 in.; lat. 40 /^ = -00158 in.; lat. 

 isthmi 5 /Lt = -0002 in. Fig. 23. I am indebted to Dr. Nordstedt 

 for a copy of Dr. Kirchner's drawing. 



24. 8. Fringsheimii Reinsch nov. var. duplo-major. A very 

 large and handsome form of this species. Eather over double the 

 size of the type. Picton, Nova Scotia. 



Long. 75-80 ix = -00295-315 in.; lat. 56-62 /j, = '0022- 

 244 in. ; lat. isthmi 22 fx = -00087 in. Fig. 24. 



DociDiuM Breb. 



25. D. occidentale nov. sp. Near to D. gracile Bailey, but 

 only about half the size of that species. Segments straight, with 

 tumid portions at regular intervals ; apex trifid, each subdivision 

 bearing a long stout spine ; the tumid processes each having a 

 double series of smaller spines, the superior pointing apically and 

 the inferior directed to the base of segment. One semi-cell only 

 seen. U.S.A. 



Long. (spin, excl.) semi-cell 150 fx, = -0059 in.; lat. corp. ^ 

 max. 17 yti = -00067 in. ; lat. spin, inch 20 4 /^ = -00079 in.; 

 lat. apicis (spin, excl.) 19 /u, = -00075 in. Fig. 25. 



The peculiarity in the setting of the spines and the simple (not 

 bifid) ends render this species very distinct from its near allies 

 gracile and verticillatwn Bail., and hidentatum Nordst. It is a 

 member of Bailey's sub-genus Trii)loceras. 



Penium Breb. 



26. P. spirostriolatum Barker. " Large, elongated, somewhat 

 attenuated in the centre, and tapering slightly towards tlio rotundo- 

 truncate ends ; tlie cell-wall possessing a number of superlicial, 

 conspicuous, rather coarse striae, running in a spiral direction ; 



