NAVICULA. 



!OI 



N. OCulata Breb ! (in Desm. ed., 1854, No. no; H.V.H. At!., 



pi. 9, f. 10*), plate 4, fig. 155. 



Valve linear-oblong, with broadly rounded apices. Central nodule sub- 

 quadrangular ; raphe surrounded by a narrow hyaline zone ; sulci approximate 

 to raphe, straight, gently incurved near the central nodule; striae finely punc- 

 tate, straight at the median portion, then becoming little by little radiate, 17 

 in 1 c.d.m. Length, 2 to 2-5 c.d.m. Breadth, about 75 c.d.m. 

 Fresh water. Brussels (Botanical Gardens, Delogne), France. 



N. elliptica Kutz. (Baa, p. 98, pi. 30, f. 55; h.v.h. Atl., pi. 10, 



f. 10*; Type No. 107), plate 4, fig. 156 (first figure). 



Valve oval-elliptic or oblong-elliptic. Raphe robust, surrounded by a rather 

 broad hyaline area, abruptly enlarged round the central nodule; sulci very 

 approximate to the raphe, following the outline of the hyaline zone ; striae 

 formed of coarse puncta, straight at the middle of the valve, and becoming 

 little by little radiate near the apices, 1 1 in 1 c.d.m. Length, 25 to 3*5 c.d.m. 

 Breadth, 1*3 to 1*5 c.d.m. 



Fresh and brackish water. Rather common throughout Europe. 



var. ovalis Hilse, plate 4, fig. 156 (second figure). 



Valve elliptic ; central nodule very large, rounded ; striae fine, 13 to 19 

 in 1 c.d.m., formed of puncta arranged in irregular longitudinal rows. 

 Length, 3-5 to 4 c.d.m. Breadth, 2 to 2-5 c.d.m. 



var. oblongella Naeg. (H.V.H. Atl., pi. 10, f. 12*, in Type No. 

 108), plate 4, fig. 157. 



Small, very elongate, about 16 striae in 1 c.d.m. Length, 2 c.d.m. 

 Breadth, -75 c.d.m. 



var. minima (H.V.H. Atl., pi. 10, f. ir ; Nav. Puellx CL), plate 4, 

 fig. 158. 



Very small, being little more than 1 c.d.m. in length. 



N. hyalina Donk. (Q.J.M.S., iS6r, p. 10, pi. i, f. 6; Brit. Diat., 

 p. 5, pi. i, f. i ; Ad. Sch. Atl., pi. 70, f. 1-4*), plate 26, fig. 754. 



Valve linear elliptic, with obtuse apices. Raphe placed in a deep sulcus, 

 abruptly attenuate near the central and terminal nodules. Striae excessively 

 delicate, 20 in 1 c.d.m., appearing marginal in axial illumination, and irregu- 

 larly bordered near the internal margin with coarse dots ; between these dots 

 and the median sulcus the valve is depressed, and in this depression the striae 



