472 BIDDULPHIA. 



Valve elliptic, lanceolate, with apices often diminuate, furnished at the 

 centre with three rather long awl-shaped spines, with coarse puncta (about 10 

 to 12 in i c.d.m.) arranged in radiating lines, about 10 to 12 in 1 c.d.m. 

 Girdle face showing at its apices the three spines and the three elevations : the 

 median of considerably less height than the terminal, the latter abruptly 

 attenuate at the apex, punctate, with puncta becoming gradually finer. Con- 

 necting zone with puncta of almost the same size as those of the valves, 

 and arranged in longitudinal lines. Frustules forming very long chains. 

 Length of valve, 3 to 8 c.d.m. 



Marine. Rather frequent. Blankenberghe, Antwerp (Scheldt), England (Kitton, Stolt., 

 Norman, Comber, Tenner, W. Sm., Roper, Okeden), Scotland (Hennedy, Greville), Ireland 

 (W. Sm., O'Meara), South Wales (Baxter Coll., No. 2815, 2816), North Wales (Shadbolt), and 

 on all the Coasts of the North Sea. 



var. minima Grun. (H.V.H. Atl., pi. 98, f. 10*), plate 20, fig. 632. 



Smaller, about 1*25 c.d.m.; puncta fine, about 14 or 15 striae in 

 1 c.d.m. 



Marine. Blankenberghe. 



var. miniscula Grun., plate 20, fig. 633. 



Very small; valve with apices longly rostrate diminuate. 



Marine. Blankenberghe. 



B. Rhombus (Ehr.) W. Sm. (S.B.D., ii., p. 49, pi. 45, f. 320; 

 pi. 61, f. 320; H.V.H. Atl., pi. 99, f. 1 and 3* ; Type No. 489), plate 20, 

 fig- 634- 



Valve rhomboidal elliptic, with apices abruptly rounded, diminuate, 

 furnished with short, awl-shaped submarginal spines of variable number ; 

 striation confused at the centre of the valve, radiant on the remainder, but 

 convergent on the portion corresponding to the apices ; stria? at the centre of 

 the valve, about 9 in 1 c.d.m., formed of coarse puncta slightly arranged in 

 quincunx. Girdle face with the middle valve portion rounded, slightly elevated, 

 processes entirely punctate, with ends gently truncate capitate. Connecting 

 membrane regularly punctate in quincunx, with puncta formed of longitudinal 

 striae, 12 to 14 in 1 c.d.m. Length of valve, 5 to 18 c.d.m. 



Marine. Rarer than the preceding. Blankenberghe, Antwerp (Scheldt), England (W. Sm., 

 Bridgman, Roper, Okeden, Kitton, Stolt., Norman, Comber), Ireland (O'Meara). On all the 

 Coasts of the North Sea. 



var. tngona Cleve. (Triceratium striolatnm (Ehr.) Roper ; H.V.H. 

 Atl., pi. 99, f. 2* ; Type No. 490), plate 20, fig. 635. 



Differs from the type-form by the triangular shape of the valves, and 

 by its three processes. 



Marine. Blankenberghe, Antwerp (Scheldt). Surface of the Dee (Stolt.), Hull 

 (Norman). Thames at Southend (Baxter Coll. No. 2577). 



