SCHIZONEMA. 



231 



impressed on the species by the abundant formation of coleoderm. I do 

 not attach any importance to the form of the fronds, and in my classification 

 of species I follow the same order as that employed for other ISiavicula. All 

 the Schizonema can, in my opinion, be reduced to a very small number of 

 type forms, and I only describe those, of whose existence as species there can 

 be no doubt. 



ANALYSIS OF SPECIES. 



Costae 



resolvable. 



No costae, 



valve 



striated. 



f Valve quite small, being only 1 c.d.rn. in length S. corymbosum. 



-., , c f Valve large, central nodule surrounded 

 Valve of ._i li- 1 1: 



several 

 c.d.m. in 



length. 



by a considerable hyaline area 



S. Smitiiii. 



Valve small, central nodule without any 



hyaline area . . .8. molle. 



' Valves furnished with an obvious pseudo-stauros . S. crucigerum. 



( Valve with strong puncta, not forming 



No 

 pseudo- 

 stauros. 



longitudinal lines 



] Strice fine, with divisions forming longi- 

 l_ tudinal lines 



S. Grevillei. 



S. ramosissimurn. 



I. Radiosse. 



N. (S.) Smithii C. Agardh. (H.V.H. Atl., pi. 15, f. 33 ; Type 

 No. 154), plate 5, fig. 241. 



Valve lanceolate, with apices somewhat produced rostrate. Raphe sur- 

 rounded by a very narrow hyaline zone dilated round the central nodule into 

 a rounded area. Stride finely divided transversely, of unequal length round 

 the central nodule ; the median ones radiate, the terminal convergent, about 

 13 in 1 c.d.m. Length, about 6 c.d.m. Breadth, 1*3 c.d.m. 



Marine. Mouth of the Scheldt (V. de Bosch). England, Scotland, Ireland, etc. 



N. (S.) molle W. Sm. ! (S.B.D., i, p. 77, pi- 58, 365; H.V.H. 

 Atl., pi. 15, f. 24*), plate 27, fig. 780. 



Valve lanceolate, with subacute apices. Striae, about 14 in 1 c.d.m., slightly 

 radiant, reaching to the raphe. Length, 3 to 4 c.d.m. 



Marine. North Sea. England (Exmouth ; Coll. W. Sm. ). 



N. (S.) corymbosum Ag. (Syst., p. uj H.V.H. Atl., pi. 15, 

 f, 21*), plate 27, fig. 780 bis. 



