100 



Navicula cruciformis, Donk. 



Navicula 



fig. 7. 



Valve linear, slightly inflated in the middle, rounded extremi- 

 ties, striiE costate, oblique, reaching to the median line ; blank 

 stauros at the central nodule. 



Hab. — Marine, scarce, Salt meadows at New Dorp. (Plate 

 XC. %. I.) 



Rabenhorst has referred this species to N. Brebissonii as a 



variety, forgetting that I described it as being a marine form ; 



moreover, it differs essentially in the structure of the valve and 



in the contour of the frustule on the side view from N. Brebissonii, 



which in this aspect is Hnear, not constricted, and narrower. 

 Don kin. 



Navicula mesolepta, var. stauroneiformis, Ehr. 



Navicula mesokpta, var. stauroneiformis. Van Heurck, p. 79, pi. VI. fig. 15. 



Valve elongated hnear; margins triundulating, forming 

 three inflations, and terminating in rounded extremities; free 

 median space with stauros at central nodule; costate striation. 



Hab.—YxQ%\^ water, frequent, but not abundant. In ponds 

 and wayside ditches in Clifton. (Plate XC. fig. 14.) 



Navicula bicapitata, Lagerst. 



Navicula bicapitata, Van Heurck Syn. Diat. Bel. pi. Vl. fig. 14 ; O'Meara, 

 Rep. on the Irish Diat. p. 352, pi. 30, fig. 32. 



Valve Hnear, terminating in constricted broadly rounded 

 apices; striation costate convergent at the centre and radiate 

 towards the extremities; not reaching the median line; free 

 space with dilation around central nodule. Hab —Fresh water. 

 Clifton. (Plate XC. fig. 3.) 



Q.J.M 



bice p. 



BaciU. p. 96. t. 28, fig. SI, which is widely different from the 

 present Gregory's specific name must therefore be dropped. 



The figure in Kiitzing is certainly not that given by Gregory ; 

 but O'Meara should have added that the drawing of Gregory 

 represents the true Navicula bicaf,ifnfn 



