NOTES ON FRESHWATER ALG^. 335 



This is a large form of S. montanum Racib. Nonn. Desm. Polon., 

 Pamietnik Akad. Umiej. w Krakowie, Wydz. Matem.-prz. x. t. xii. 

 f. 11 (1885). Tiie latter, however, appears to be only a stout small 

 form of S. fuscigerum Breb., and should be called var. montanum 

 (Racib.). 



26. Arthrodesmus hexagonus Boldt, var. tetraspinosus Schroder. 

 I. c. 29, t. iii. f. 5 (1897). This is a rounded form of Xanthidium 

 concinnum Arch. var. Boldtiana West in Journ. Linn. Soc. hot. 

 xxix. 167, pi. xxii. f. 6 (1892). We think there is need to emphasize 

 the fact that Arthrodesmus hexagonus Boldt (1885) is identical with 

 Xanthidium concimium Arch. (1883), and also that Archer placed the 

 plant under the correct genus. We have recently given good figures 

 of X. concinnum (Cfr. Journ. Roy. Micr. Soc. 1897, pi. vi. f. 15). 



27. Arthrodesmus Lapezynskii Gutw. in Rosprawy Akad. Umiej. 

 Krakow. Wydz. mat.-przyr. t. xxxiii. 57, t. vii. f. 68, 1896. This 

 seems to us but a variety of A. octocornis Ehrenb. possessing a few 

 minute additional spines. The sides of the semicells are not more 

 retuse than those of many forms of A. octocornis, especially 

 American forms. 



28. Selenosph^rium Hathoris Cohn, in Festschr. d. Naturf. 

 Ges. zu Halle, t. xi. f. 16, 17, 1879. 



Hab. Harvey Lake, Pa., U.S.A. 



These were very fine specimens, and formed large coenobia. 



29. Dactylococcus bicaudatus A. Br. var. subramosum, var. n. 

 Var. minor, cellulis minus attenuatis, concatenatis et subramosis. 

 Crass, cell. 3-8-6-5 {x. 



Hab. Forming a green stratum on dripping rocks, Mossdale 

 Moor, Widdale Fell, N. Yorkshire. 



30. Scenedesmus spicatus, sp. n. S. cellulis plerumque 

 binis, ellipticis, diametro circiter 2 plo longioribus, supra marginem 

 exterior! serie spinarum brevium 6-7 pr£editis. Long. cell. 7*5-9 /x; 

 lat. cell. 4 [x; long. spin. 2-2*5 /x. 



Hab. In a pond, Saltburn, N. Yorkshire. 



31. Rhaphidium polymorphum Fresen. var. spirale, var. n. 

 Var. cellulis solitariis, spiraliformibus, anfractibus 1-1-| ; apiculis 

 acutissimis. 



Hab. Hawksworth, W. Yorkshire ; in immense quantity amongst 

 Myriophyllum spicatum. Also Pilmoor, near Thirsk, N. Yorkshire. 



32. Oocystis parva, sp. n. 0. minuta; cellulis plerumque 

 solitariis vel in familiis 2-4 cellularum consociatis ; cellulis ple- 

 rumque oblique ellipsoideis, 1|— If-plo longioribus quam latioribus, 

 apicibus subacutis et non incrassatis; membranafirma. Contentum 

 chlorophyllosum cellularum in massis parietalibus 2-3. Long. cell. 

 6-12 /x; lat. cell. 4-7 /x ; long. teg. 13-5-29 /x ; lat. 10-5-18 /x. 



Hab. Pilmoor, near Thirsk, N. Yorkshire ; abundant in pools. 



This species occurred in quantity amongst other small algae, and 



appears to be distinctive ; its small size, its somewhat obliquely 



elliptical cells, and its few chromatophores distinguish it. The 



