20 EUCRATIID^E. 



stones at extreme low-water mark (M. Sars) : Little Belt, 

 near Fanoe, 10-26 fms. (Kirclien2)auer) : Sable Island 

 (G. Willisii) (Dawson) : Labrador, 15 fms. (Wallich) : 

 St. George's Banks, 50-85 fms. (Smith & Harger) : White 

 Sea (Mereschkowsky) : Ostend (Van Ben.). 



The most striking characteristic, perhaps, of this species 

 is the perfect simplicity of its structure. There is no 

 complexity in the arrangement of the parts ; the general 

 plan is plain and definite and singularly free from varia- 

 bility. There are no accessory appendages ; even the radi- 

 cal fibres, which are generally very susceptible of modifi- 

 cation, are of the most rudimentary type. 



The cells are at times more elongated below; and there 

 are slight differences of form, dependent on the degree 

 in which the aperture slopes upward. From about the 

 middle of the front surface, where the cell is thickest, it 

 narrows gradually towards the base ; and from the same 

 point the aperture slants more or less obliquely to the 

 top. The pairs of cells rise immediately one from the 

 other, each cell taking its origin at the back of the one 

 below it, just behind the aperture, as in the genus 

 Eucratea. The branches are given ofi" from each side of 

 the uppermost pair in a stem, close to the top ; and at 

 times the stem ascends between them, and a triplet is 

 formed in place of the more usual bifurcation. The 

 shoots rise from a trailing bundle of intertwining fibres of 

 considerable thickness, and are themselves composed to- 

 wards the base of many tubular strands, some of which 

 are carried up along the lower portion of the branches. 

 There is a very great development of the radiciform 

 fibres. 



Alder mentions two varieties of this species — " the one 

 rather more rigid, darker-coloured, and with the branches 



