Fresh-wafer Algse, &c. By A. W. Bennett. 17 



Euastrum erosum Lund. 

 „ insulare Wittr. 

 „ binale Breb. 

 *EuASTEUM CRENULATUM h. sp. Figs. 20 and 21. 



Frond very minute. Each frustule 25 //. long by 11 ^tt deep, 

 broadest at apex; with two teeth at each outer angle and one at 

 the base; sides concave; apical edge with three concave crenations, 

 of which the centre one is the largest. Isthmus 7 fji wide and deep, 

 with a broad sinus on each side. Each frustule with three prominent 

 protuberances. 



Bog pools, not uncommon. This pretty desmid does not seem to 

 come very near to any other species with which I am acquainted. The 

 appearance presented by the end view indicates its right place in 

 Euastrum. The front view strikingly resembles Staurasfrum Eenardii 

 Eeinsch ; but the end view is totally different. Cosmarium Begnesii 

 Eeinsch is also somewhat similar in outline. 



Cosmarium cucumis Corda. 



„ pyramidatum Breb. 



„ crenatum Kalfs. 



„ undulatum Corda. 



„ tetraophthalmum Ktz. 



„ botrytis Bory. 



„ margaritiferum Turp, 



„ Brebissonii Menegh. 



„ speciosum Lund. 



*C0SMAEIUM SPHERICUM n. sp. Fig. 22. 



Frond moderately large. Frustules very nearly spherical, about 

 45 /x. long and broad, covered with very prominent projections, which 

 give them a very deeply crenulated edge ; sinus rather deep. Endo- 

 chrome very dark green. 



The frustules of this very beautiful desmid are more nearly spherical 

 than those of any other species of nearly the same size. It is further 

 distinguished by the very conspicuous papillae which cover the whole 

 surface, resembling those of C. cristatum Kalfs, and by the deep green 

 of the abundant endochrome. It comes near to C. Brebissonii Menegh., 

 but the frustules are more nearly spherical, and to G. Logiense Biss. 

 (Joum. Pt. Micr. Soc, 1884, p. 194, t. v. f. 4), but the description of 

 the latter is hardly full enough for identification ; C. orhiculatum Ealfs 

 is considerably smaller. I found it not unfrequently in gatherings 

 from bog pools. 



Cosmarium coelatum Ealfs. Common. 



„ ornatum Ealfs. 



„ cristatum Ealfs. 



„ cucurbita Breb. 



* „ Broomei Thw. Bog pool, St. Denis. 



*C0SMAEIUM DISCRETUM n. sp. Fig. 23. 



Frond small. Frustules nearly semi-elliptical or slightly reniform, 

 37"5 /i by 17'5 //., rough with pearly granules. Isthmus very con- 

 1887. 



