TR0PID0NE1S. 



265 



PI. elegans (W. Sm.) Grun. 



(Amphiprora ekqans W. Sm., S.B.D., ii., 

 p. 90; H.V.H. Atl., pi. 22, f. 1 and 6*; 

 Type No. 199), plate 6, fig. 294. 



Valve lanceolate, narrow, very convex. 

 Lateral plait very visible on the girdle 

 side throughout the length of the valve. 

 Striae about 13 in 1 c.d.m., very visible, 

 granular, leaving a small hyaline area 

 round the central nodule. Girdle face 

 sub-quadrangular, with rounded apices. 

 Length, 20 to 30 c.d.m. 



Marine. Rare. Washing of mussels (Deby), 

 Blankenberghe (H.V.H.), England (W. Sm. ; Kitton), 

 Scotland (Greg.), Ireland (W. Sm.). 



Fig. 54- 

 Plagiotropts elegans. 



PI. Van Heurckii Grun. (H.V.H. Atl, pi. 22 bis., f. 6, 7, 8* 

 Type No. 198), plate 6, fig. 295. 



Valve lanceolate, with apices strongly tapering. Lateral plait abruptly 

 arcuate from the third of the valve, and only distinctly visible (in girdle 

 view) on the terminal third of the frustule. Striae very delicate, about 22 in 

 1 c.d.m. Girdle face quadrangular, sub-elliptic, with median portion scarcely 

 constricted. Length, about 6 c.d.m. 



Marine. I made an abundant gathering of this interesting species in the spring and autumn 

 of 1882 in the Retaining Basin of Blankenberghe. I had not previously noticed it. 



PI. vitrea (W. Sm.) Grun. (Arct. D., p. 67; h.v.h. Atl., 

 pi. 22, f. 7-9*), plate 29, fig. 805. 



Valve lanceolate, with keel very eccentric, central nodule rather small, 

 transverse striae fine, 17 to 19 in 1 c.d.m. Girdle face lanceolate, subtruncate, 

 without any constriction. Length, 7^5 to io - 5 c.d.m. Breadth of valve, 1-5 

 to about 2 c.d.m. Breadth of frustule, 8*5 to 14*5 c.d.m. 



