384 APPENDIX. 



1. Didymia simplex, n. sp. Tab. i. fig. 6. 



Cells oblong, narrowed below, broad and truncate, with 

 an angle externally above. Back marked with transverse 

 rugae. 



Hab. — Bass Strait, 45 fathoms. 



A fine species, growing ia loosely-branched phytoid 

 fronds, to a height of several inches. In some (dried) 

 specimens the branches are a little incurved, but not in all. 

 The situation of the ovicell is peculiar. It is contained 

 within the upper part of a cell placed between, or rather in 

 front of the pair, from which the two branches at a bifur- 

 cation take their origin. The ovigerous cell differs widely 

 in form from the others, being pyriform, and much 

 attenuated below; and the orifice is below the middle. 

 The upper compartment, iu which the oviceU or sac itself 

 is lodged, appears to be separated from the lower by a 

 transverse diaphragm, 



23. DiMETOPiA, n. gen. Tab. i. fig. 7 — 9- 



Cells joined back to back ; the mouths of each alternate 

 pair looking iu the same direction, and at right angles to 

 the intermediate pair. 



1. D. spicata, n. sp. Tab. i. fig. 9. 



Cells infundibuhform. Margin of opening much thick- 

 ened, with sis equidistant, elongated pointed spines. 



Hab. — Bass Strait, 45 fathoms. 



White, transparent, forming thick tufts about li to 2 

 iuches in height. The same species also occurs in New 

 Zealand. 



2. D. cornuta, n. sp. Tab. i. fig. ^, 8. 



Cells suddenly contracted about the middle. Opening 

 oval, wide above; margins slightly thickened with a 

 short thick conical horn on each side above, and a long 

 projecting spine (rarely two) in front below. 



Hab. — Bass Strait, 45 fathoms. 



Branches narrower than in the preceding species. Colour 



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