PLEUROSIGMA. 253 



PI. intermedium W. Sm. (S.B.D., L, p. 64, pi. 21, f. 200; 

 H.V.H. Atl., p. 18, f. 6*; Type No. 174), plate 6, fig. 267. 



Valve lanceolate, narrow, with margins almost straight ; raphe scarcely 

 sigmoid. Transverse stria? 21 to 23, oblique strice 20 to 22 in 1 c.d.m. 

 Length, 15 to 30 c.d.m. 



Mr. Grunow remarks that the short are more distinctly sigmoid than the 

 longer specimens. 



Marine. This species has not yet been found in Belgium, but has been frequently so in England, 

 France and Holland. It approaches PL delicatulum, and may also be considered as a form of 

 PI. angulatum. 



var. Nubecula. (PI. Nubecula W. Sin.) 



Only differs from the type form by its smaller size and more obtuse 

 apices ; the striation is identical. 



* * STRIDE OBLIQUE, CUTTING ONE ANOTHER AT AN ANGLE OF MORE 



THAN 6o. 



PI. Speciosum W. Sm. (Ann. N.H., 1852, p. 5, pi. i, f. 5 ; 

 S.B.D., i., p. 63, pi. 20, f. 197 ; Perag., pi. 2, f. 16*; H.V.H. in Type No. 

 170), plate 28, fig. 793. 



Valve linear-lanceolate, with apices slightly curved, rounded. Raphe 

 straight, parallel to margins, being abruptly bent quite close to the apices. 

 Transverse striae 19-20, oblique striae 16-18 in 1 c.d.m. Length, 21 to 39 

 c.d.m. Breadth, 2 '5 c.d.m. 



Marine. England (W. Sm.). Ireland (O'Meara), and probably also other countries. 



PI. elongatum W. Sm. (Ann. N.H., 1852, p. 6, pi. 1, f. 4; 



S.B.D., i., p. 64, pi. 20, f. 199; H.V.H. Atl., pi. 18, f. 7*; Type No. 

 173), plate 6, fig. 262. 



Valve very long and very narrowly lanceolate, with striae crossing one 

 another at an angle of about 68. Length, 21 to 38 c.d.m. Breadth, about 

 3 c.d.m. 



Antwerp (Scheldt, where it is rather frequent). Blankenberghc. England (Comber, Norman, 

 Kitton, Stolt.). Ireland (O'Meara) and probably on all the coasts of the North Sea. 



In my Synopsis I referred this form to the angulatum with which it is 

 closely connected. 



